The role of pacemaker algorithms in preventing atrial fibrillation progression

Mahmoud Shawky Abdelmoneum, Hesham Mohamed Aboul-Enein, Abdelhakeem Samir Abdelhakeem, Wael Ahmed Elsayed Makled, Mohammed Saeed Darwish. The role of pacemaker algorithms in preventing atrial fibrillation progression. Cardiometry; Issue 23; August 2022; p. 64-75; DOI: 10.18137/ cardiometry.2022.23.6475; Available from:

In patients without atrioventricular (AV) block, unnecessary right ventricular (RV) pacing has been shown to be detrimental, causing cardiac dyssyn-chrony and increasing the risk of developing permanent atrial fibrillation (AF) (Nielsen et al., 2011). A linearly increasing relationship between the cumulative percentage of RV apical pacing (CumVP%) and the risk of AF has been demonstrated (Sweeney et al., 2003). Recent studies have shown that RV apical pacing impacts adversely on left atrial (LA) structure and function and that this may trigger new-onset atrial arrhythmias (Pastore et al., 2014). Therefore, algorithms to minimize ventricular pacing have been added to the DDD/DDDR pacing modes. However, recent studies and a meta-analysis (Shurrab et al., 2017) did not convincingly confirm the superiority of atrial pacing and sensing, or of RV pacing minimization, in comparison with standard DDD/DDDR pacing, in improving clinical outcomes in pacemaker (PM) patients. Indeed, there is now growing evidence that a long PR is associated with a higher risk of AF and poor prognosis (Nielsen et al.,2012). Progression to persistent AF (PeAF) is prevented by minimizing RV pacing in patients with normal PR and by standard dual-chamber pacing in those with long PR (Boriani et al., 2019).

The current standard of care in patients with sinus node disease (SND) on dual-chamber pacing is programming the PM with a long AV delay or with specific algorithms to minimize ventricular pacing. However, many patients with SND who require PM implantation also show a concomitant prolongation of AV conduction (Brignole et al.,2013). This AV management exaggerates the AV delay due to the intra/ interatrial conduction delay caused by standard atrial pacing and concomitant drug use.

Study design and population

This retrospective cohort study was conducted over 1 year period from July 2021 to July 2022 and was performed in BenhaUniversity Hospital, Nasr City Hospital for Health Insurance, and Benha teaching hospitals on 120 patients with dual and single chamber pacemakers.

There were two groups with DDDR mode in Group A (60 patients) and VVVIR in Group B (control group) (60 patients) and all patients have intermittent heart block or SND. And paramaters for minimization of V pacing such as VIP in Group A and hysteresis Group B will be linked with AF. Also patients characteristics, cause of implantation, date of implantation and RV lead position were linked to that risk.

Inclusion Criteria: Patients aged ≥18 years who had an indication for VVI or DDD permanent pacemaker implantation based on current guidelines and underwent successful initial dualchamber or single chamber permanent pacemaker implantation qualified for enrollment.

Exclusion criteria Patients with valvular heart disease involving the mitral or aortic valve (moderate or severe stenosis or regurgitation), a history of open heart surgery within the past 6 months, a known history of persistent or permanent AF at initial implant, ejection fraction lower than 50%, diastolic dysfunction grade II or moreor any of its risk factors (IHD, DM HTN, CKD, obese patients and smokers), left atrium diameter more than 4cm, a history of an atrioventricular node ablation or AF ablation, and those patients with a cardiac resynchronization therapy device implant were excluded.

All patients were subjected for the following

Full history and Clinical evaluation: to collect the basic clinical data of the patient including the following: - Personal data: Age, gender, history of pacemaker implantation and vital signs at time of arrival: blood pressure, the heart rate, respiratory rate.

• 12 Lead ECG. The resting 12 lead ECG was done to assess any signs of arrhythmias, heart blocks or ischemia.

AF classification (ESC guidlines 2020).

Paroxysmal AF: AF terminating spontaneously or with intervention within 7 days of onset.

Persistent AF: Continuous AF lasting ≥7 days.

Longstanding persistent AF: Continuous AF lasting ≥12 months.

Permanent AF: AF for which patients and clinicians chose not to employ a rhythm control strategy.

Full labs: CBC, urea,creatine, Na, K, INR, ALT and AST.

Conventional echocardiographic study Routine 2D and M.mode echography were used to assess ejection fraction, regional segmental wall motion abnormalities and significant valve lesions, diastolic function and left atrium diameter.

Pacemaker interrogation

• •    Type of pacemaker either single chamber or dual chamber.

• •    Type of the device St Jude all patients.

• •    Type of the lead (bibolar) for all patients in our study.

• •    Pace maker parameters.

→Rate adaptive usually for all patients.

→Hysteresis either on or off usually set on for patient having intrinsic rhythm for minimization of ventricular pacing.

→AV delay (in dual chamber pacemakers) set as the default pacedAV delay between 125 to 200 ms and sensed AV delay usually shorter by about 25 to 50 ms except in patients with intrinsic rhythm we need more prolongation for minimization of ventricular pacing.

→PVARP set as the default (250 to 300 ms). Starts with a sensed or paced ventricular event and defines a period on the atrial channel during which a spontaneous atrial event is not tracked. It serves multiple important roles critical to DDD pacing, including avoiding pacemaker-mediated tachycardia (PMT).

→VIP mode in dual chamber pacemaker group either on or off. Ventricular intrinsic preference (VIP) algorithm extends the AV delay (Jankelson et al., 2019).

Over 1–3 intervals in order to promote the return of intrinsic conduction with maximal allowed AV delay 450 ms.

Sensing of the atrial and ventricular events.

→Pulse width.

→Lead impedence.

→Pulse threshold.

→Auto capture set on after the 1 month of implantation to performed by closed-loop feedback algorithms that periodically measure the pacing threshold and adjust the output. When performed on a beat-to-beat basis,it can conserve battery by delivering safe pacing with an output minimally above the pacing threshold.

→Automatic mode switch set on for prevention of the ventricle from tracking high atrial rates. (in dual chamber pacemakers).

→Ventricular pacing percentage. (in dual chamber and single chamber pacemakers)

→Atrial pacing percentage (in dual chamber pacemakers).

→Atrial high rate episodes (AHRE) Device-programmed rate criterion for AHRE is >_175 bpm, whereas there is no specific rate limit for subclin-ical AF. The criterion for AHREduration is usually set at >_5 min (mainly to reduce the inclusion of artefacts), whereas a wide range of subclinical AF duration cutoffs (from 10 - 20 seconds to >24 hours) is reported in studies of the association of subclinical AF with thromboembolism it is number and duration manually reviewed to show it is either artifact or true atrial high rate. (in dual chamber pacemakers). and then classified as Subclinical AF (if not documented by ECG), atrial tachycardia, atrial flutter and SVT.

Fluroscope was used for localization of the RV lead position.

Statistical analysis: Data were collected, revised, coded and entered to the Statistical Package for Social Science (IBM SPSS) version 23. The quantitative data were presented as mean, standard deviations and ranges when parametric and median, inter-quartile range (IQR) when data found non-parametric. Also qualitative variables were presented as number and percentages. The comparison between groups regarding qualitative data was done by using Chi-square te-stand/or Fisher exact test when the expected count in any cell found less than 5. The comparison between two independent groups with quantitative data and parametric distribution was done by using Independent t-test while with non-parametric distribution were done by using Mann-Whitney test.

Spearman correlation coefficients were used to assess the correlation between two quantitative parameters in the same group. Univariate and Multivariate logistic regression analysis was used to assess predic- tors of developing AF in each group. The confidence interval was set to 95% and the margin of error accepted was set to 5%. So, the p-value was considered significant as the following:

P-value > 0.05: Non significant (NS)

P-value < 0.05: Significant (S)

P-value < 0.01: Highly significant (HS)

RESULTS

General characteristics in both groups

Group A included 60 patients with mean age was 62.93± 10.47, 56.7%% of patients were males and 51.7%) females. Group B included 60 patients with mean age 64.35 ± 12.51, 80.0% of patients were males and 43.3%% females and there was no significant difference of demographic data between both groups, table 1.

Echocardiography in both groups

Patients only with normal EF, diastolic function and LA diameter were included with no significant difference between the two groups, table 2.

Cause, date and rhythm of implantation, lead position and parameters in the two groups

Pacemaker data as regards cause of implantation, date of implantation, RV lead position, RV parameter sand RV pacing (%) were not assossiated with significant difference between the two groups, table 3.

AF in both groups

Difference between the two groups as regards, the total number of AF patients which were more in Group B with no significant difference between the two groups.Also AF type with higher prevalence of paroxysmal AF in Group A with high significant difference P value < 0.001.And Permanent AF which was more in group B with high significant difference P-value <0.001, table 4.

Table 1

General characteristics in both groups

		Group A	Group B	Test value	P-value	Sig.
		No. = 60	No. = 60
Age (years)	Mean±SD	62.93±10.47	64.35±12.51	-0.673•	0.503	NS
	Range	29 – 82	42 – 87
Sex	Female	31 (51.7%)	26 (43.3%)	0.835*	0.361	NS
	Male	29 (48.3%)	34 (56.7%)

Table 2

Echocardiographic data in both groups

		Group A	Group B	Test value	P-value	Sig.
		No. = 60	No. = 60
LA diameter	Mean ± SD	3.37 ± 0.37	3.40 ± 0.35	-0.428•	0.670	NS
	Range	2.8 – 4	2.8 – 4
EF %	Mean ± SD	58.10 ± 5.76	58.70 ± 5.61	-0.578•	0.565	NS
	Range	50 – 70	50 – 71
Diastolic function	Normal	26 (43.3%)	24 (40.0%)	0.137*	0.711	NS
	Grade I	34 (56.7%)	36 (60.0%)

P-value > 0.05: Non significant; P-value < 0.05: Significant; P-value < 0.01: Highly significant

• •: Independent t-test

LA left atrium. EF: Ejection fraction.

Table 3

Cause, date and rhythm of implantation, lead position and parameters in the two groups

		Group A	Group B	Test value	P-value	Sig.
		No. = 60	No. = 60
Cause of implantation	CHB	45 (75.0%)	44 (73.3%)	3.385*	0.496	NS
	SSS	13 (21.7%)	12 (20.0%)
	Vagal	1 (1.7%)	2 (3.3%)
	2nd HB	0 (0.0%)	2 (3.3%)
	1st HB	1 (1.7%)	0 (0.0%)
Date of implantation (years)	Median (IQR)	4 (2 – 7)	5.5 (1.85 – 10)	-1.425≠	0.154	NS
	Range	0.33 – 18	0.5 – 30
Rhythm at implantation	Sinus, 3rd degree HB	43 (71.7%)	48 (80.0%)	1.137*	0.286	NS
	SND	16 (26.7%)	10 (16.7%)	1.768*	0.184	NS
	Sinus, 2nd degree HB	0 (0.0%)	2 (3.3%)	2.034*	0.154	NS
	Sinus,1st HB	1 (1.7%)	0 (0.0%)	1.008*	0.315	NS
RV lead position	Apical	33 (55.0%)	43 (71.7%)	3.589*	0.058	NS
	Non apical	27 (45.0%)	17 (28.3%)
RV pacing (%)	Median (IQR)	35 (13 – 68.5)	46 (24.5 – 78.5)	-1.762≠	0.078	NS
	Range	0.1 – 90	1 – 90
RV lead Impedance	Median (IQR)	491.5 (434 – 559)	528.5 (450 – 614)	-1.181≠	0.238	NS
	Range	350 – 1090	174 – 6200
RV IR	No	24 (40.0%)	28 (46.7%)	0.543	0.461	NS
	Yes	36 (60.0%)	32 (53.3%)
RV Sense	Median (IQR)	10 (5 – 12)	9 (5 – 11.65)	-0.057≠	0.954	NS
	Range	0.5 – 15	2 – 15
RV Threshold	Median (IQR)	0.75 (0.75 – 1)	1 (0.75 – 1)	-0.572≠	0.567	NS
	Range	0.5 – 4	0.5 – 2.75
P-width	Median (IQR)	0.4 (0.4 – 0.4)	0.4 (0.4 – 0.4)	-0.635≠	0.525	NS
	Range	0.4 – 1	0.4 – 1

P-value > 0.05: Non significant; P-value < 0.05: Significant; P-value < 0.01: Highly significant

• *: Chi-square test; ≠: Mann-Whitney test

CHB: complete heart block, SSS: sick sinus syndrome, HB: heart block, RV: right ventricle, IR: intrinsic rhythm P-width pulse width.

Table 4

Types of AF in the two groups.

		Group A	Group B	Test values	P-value	Sig.
		No. = 60	No. = 60
AF	No AF	47 (78.3%)	38 (63.3%)	3.267*	0.071	NS
	AF	13 (21.7%)	22 (36.7%)
AF Type	Paroxysmal	12 (92.3%)	2 (9.1%)	23.578*	0.000	HS
	Permanent	0 (0.0%)	15 (68.2%)	15.511*	0.000	HS
	Persistent	1 (7.7%)	5 (22.7%)	1.300*	0.254	NS

P-value > 0.05: Non significant; P-value < 0.05: Significant; P-value < 0.01: Highly significant

*: Chi-square test

AF atrial fibrillation.

Group A

• 1-    Patients charactarestics in group A

As regards age increased age had high significance for developing AF with P value< 0.001, male sex was more risky than female for developing AF with significant difference and P value 0.020.

• 2-    Echocardiography in group A

Also EF and LA which were in normal values had no significant difference in AF development.

• 3-    Pace maker parameters in group A

As regards pacemaker parameters the PVARP which were set to the nominal levels, AV delay (paced and sensed) and ventricular lead position had no significance in AF development.

As regards RV pacing percentage increasing that value had high significance for developing AF with P value P <0.001, also A pacing had high significance for developing AF with P value <0.001and VIP mode on is protective of unnecessary RV pacing and so decreasing the risk of AF so with VIP mode s OFF there was high significance of developing AF with P value <0.001, table 5.

• 4-    Atrial high rate episodes and the relation with AF .

As regards AHRE It had high significance with AF development with p value <0.001 and as a regards

Table 5

Patients charactarestics, causes of implantation, echo-cardiograghy, pacemaker parameters and its relation with AF in group A.

		AF		Test value	P- value	Sig.
		No AF	AF
		No.= 47	No.= 13
Age (years)	Mean ± SD	60.34 ± 10.20	72.31 ± 4.37	-4.108•	0.000	HS
	Range	29 – 82	65 – 81
Sex	Female	28 (59.6%)	3 (23.1%)	5.432*	0.020	S
	Male	19 (40.4%)	10 (76.9%)
LA diameter	Mean ± SD	3.33 ± 0.38	3.52 ± 0.32	-1.657•	0.103	NS
	Range	2.8 – 4	2.8 – 3.9
EF %	Mean ± SD	58.23 ± 5.83	57.62 ± 5.71	0.340	0.735	NS
	Range	50 – 70	50 – 66
PVARP	Mean ± SD	268.62 ± 17.65	267.31 ± 21.37	0.226•	0.822	NS
	Range	250 – 300	250 – 300
Cause of implantation	3rd degree CHB	38 (80.9%)	7 (53.8%)	3.961*	0.047	S
	SND	7 (14.9%)	6 (46.2%)	5.863*	0.015	S
	Vagal	1 (2.1%)	0 (0.0%)	0.281*	0.596	NS
	2nd degree HB	0 (0.0%)	0 (0.0%)	–	–	–
	1st degree HB	1 (2.1%)	0 (0.0%)	0.281*	0.596	NS
Date of implantation (years)	Median (IQR)	3 (1 – 6)	9 (4.5 – 11.5)	-3.478≠	0.001	HS
	Range	0.33 – 14	1 – 18

		AF		Test value	P- value	Sig.
		No AF	AF
		No.= 47	No.= 13
RV lead position	Apical	24 (51.1%)	9 (69.2%)	1.358*	0.244	NS
	Non apical	23 (48.9%)	4 (30.8%)
RV pacing (%)	Median (IQR)	28 (9 – 49)	70 (69 – 89)	-4.694≠	0.000	HS
	Range	0.1 – 87	50 – 90
Paced AV delay	Mean ± SD	189.36 ± 24.31	176.92 ± 18.99	1.703•	0.094	NS
	Range	125 – 225	150 – 200
Sensed AV delay	Mean ± SD	154.26 ± 22.91	146.15 ± 13.87	1.210•	0.231	NS
	Range	100 – 200	125 – 175
VIP	On	41 (87.2%)	3 (23.1%)	21.434	0.000	HS
	Off	6 (12.8%)	10 (76.9%)
A pacing	Median (IQR)	19 (15 – 27.1)	80 (77 – 88)	-5.460≠	0.000	HS
	Range	11 – 62	66 – 90

P-value > 0.05: Non significant; P-value < 0.05: Significant; P-value < 0.01: Highly significant

*: Chi-square test; •: Independent t-test; ≠: Mann-Whitney test

AV delay atrioventricular delay, VIP ventricular intrinsic preference, PVARP post ventricular absolute refractory period, A pacing atrial pacing, RA right atrium, P-width pulse width, HB heart block, SND sinus node disease its sub types subclinical AF had high significance for developing AF with value <0.001. Other subtypes AT, SVT had no significance for AF development. Also as regards the duration of AHRE there was high significance of developing AF with increased duration of AHRE with Median (IQR) 70 (50 - 130) p value 0.001. The number of AHRE had no significance with AF development with p value 0.056, table 6.

• 5-    Univariate logistic regression analysis for the risk variables shows that:

• -    Age >69 years was associated with significant AF risk p value <0.001 (OR) 26.812

• -    Male gender was associated with significant AF risk p value 0.028 (OR) 4.912

• -    Rhythm at implantation (SND) was associated with significant AF risk p value 0.021(OR) 4.898

Table 6

AHRE subtypes, duration and it is significance in AF development

		No AF	AF	Test value	P-value	Sig.
		No. = 47	No. = 13
AHRE	Negative	37 (78.7%)	0 (0.0%)	26.698*	<0.001	HS
	Sub-clinical AF	4 (8.5%)	12 (92.3%)	36.566*	<0.001	HS
	SVT	2 (4.3%)	0 (0.0%)	0.572*	0.449	NS
	AT	3 (6.4%)	0 (0.0%)	0.873*	0.350	NS
	Sub-clinical AF and SVT	0 (0.0%)	1 (7.7%)	3.677*	0.055	NS
	Sub-clinical AF and AT	1 (2.1%)	0 (0.0%)	0.281*	0.596	NS
No. of AHRE	Median (IQR)	2 (1 – 3)	4 (2 – 5)	-1.908≠	0.056	NS
	Range	1 – 3	1 – 6
Duration of AHRE	Median (IQR)	5 (4 - 6)	70 (50 - 130)	-3.207≠	0.001	HS
	Range	2 – 8	30 – 180
No. of sub-clinical AF	Median (IQR)	2 (2 – 2)	3 (2 – 5)	-0.899≠	0.368	NS
	Range	2 – 2	1 – 6
No. of SVT	Median (IQR)	2.5 (2 – 3)	2 (2 – 2)	-0.707≠	0.480	NS
	Range	2 – 3	2 – 2

AHRE atial high rate episodes, SVT supraventriculat tachycardia, AT atrial tackycardia, AF atrial fibrillation

• -    Date of implantation >3 years was associated with significant AF risk p value 0.010 (OR) 16.200 VIP (Off) was associated with significant AF risk p value 0.000 (OR) 22.778

• -    No IR was associated with significant AF risk p value 0.021(OR) 4.800 AHRE (Sub-clinical AF) was associated with significant AF risk p value 0.000 (OR) 9.879

• -    Cause of implantation (SND) was associated with significant AF risk p value 0.001 (OR) 129.000

• 6- Multivariate logistic regression analysis we found that the most important two variables with higher risk were Date of implantation >3 years p-value 0.010 Odds ratio 52.444 and VIP (Off) p value 0.001 odds ratio 62.919, table 7.

Aging Mean ± SD 73.27 ± 7.55 had high significant risk for developing AF with p value < 0.001. Male sex had significant risk for developing AF with p value 0.014.

Group B (control group)

• 1 - Patients characteristics and it is relation with AF in group B.

Aging Mean ± SD 73.27 ± 7.55 had high significant risk for developing AF with p value<0.001. Male sex had significant risk for developing AF with p val-ue0.014, table 8.

2-Echocardiography, cause of implantation, date of implantation and pacemaker parameters and its relation with AF.

As regards LA diameter and EF (in normal values) had no significant risk for AF development.

As regards 3 ^rd degree heart block had high significant risk for developing AF with p value0.002 and also SND had high significant risk for developing AF with p value0.002. Date of implantation with Median (IQR) 9.25 (5.5 – 12) had high significant risk for developing AF with p value < 0.001. RV lead position either apical or non apical had no significant risk for AF development. As regards RV pacing (%) Median (IQR) 79 (69 – 89) had high significant risk for developing AF with p value < 0.001. Also hysteresis off had high significant risk for developing AF with p value < 0.005, table 9.

3-Using univariate logistic regression analysis.

Table 7

Univariate and multivariate logistic regression analysis for factors associated with AF among group A.

	Univariate				Multivariate (Backward: Wald)
	P-value	Odds ratio (OR)	95% C.I. for OR		P-value	Odds ratio (OR)	95% C.I. for OR
			Lower	Upper			Lower	Upper
Age >69 years	0.000	26.812	4.958	144.989	–	–	–	–
Male gender	0.028	4.912	1.193	20.234	–	–	–	–
Cause of implantation (SND)	0.021	4.898	1.264	18.973	–	–	–	–
Date of implantation >3 years	0.010	16.200	1.944	135.013	0.007	52.444	3.021	910.428
VIP (Off)	0.000	22.778	4.841	107.181	0.001	62.919	5.999	659.946
No IR	0.021	4.800	1.272	18.111	–	–	–	–
AHRE (Sub-clinical AF)	0.000	129.000	13.157	1264.757	–	–	–	–
Rhythm at implantation (SSS)	0.001	9.879	2.435	40.076	–	–	–	–

SND sinus node disease, VIP ventricular intrinsic preference, AHRE atrial high rate episode, SSS sick sinus syndrome.

Table 8

Patient characteristics and it is relation with AF

		AF		Test value	P-value	Sig.
		No AF	AF
		No.= 38	No.= 22
Age (years)	Mean ± SD	59.18 ± 11.94	73.27 ± 7.55	-4.979•	0.000	HS
	Range	42 – 82	58 – 87
Sex	Female	21 (55.3%)	5 (22.7%)	6.007*	0.014	S
	Male	17 (44.7%)	17 (77.3%)

P-value > 0.05: Non significant; P-value < 0.05: Significant; P-value < 0.01: Highly significant

*: Chi-square test; •: Independent t-test; ≠: Mann-Whitney test

Table 9

Echocardiography, cause of implantation, date of implantation and pacemaker parameters and its relation with AF

		No AF	AF	Test value	P-value	Sig.
		No. = 38	No. = 22
LA diameter	Mean ± SD	3.43 ± 0.36	3.35 ± 0.34	0.786	0.435	NS
	Range	2.8 – 4	2.8 – 3.9
EF %	Mean ± SD	58.87 ± 5.99	58.41 ± 5.01	0.303•	0.763	NS
	Range	50 – 70	51 – 71
Cause of implantation	CHB	33 (86.8%)	11 (50.0%)	9.671*	0.002	HS
	SND	3 (7.9%)	9 (40.9%)	9.492*	0.002	HS
	Vagal	2 (5.3%)	2 (9.1%)	1.198*	0.274	NS
	2nd HB	0 (0.0%)	0 (0.0%)	–	–	NS
	1st HB	0 (0.0%)	0 (0.0%)	–	–	NS
Date of implantation (years)	Median (IQR)	3 (1.1 – 7)	9.25 (5.5 – 12)	-4.323	0.000	HS
	Range	0.5 – 11	4 – 30
RV lead position	Apical	27 (71.1%)	16 (72.7%)	0.019*	0.890	NS
	Non apical	11 (28.9%)	6 (27.3%)
RV pacing (%)	Median (IQR)	29 (20 – 43)	79 (69 – 89)	-5.137	0.000	HS
	Range	1 – 80	1 – 90
Hysteresis	On	33 (86.8%)	12 (54.5%)	7.751*	0.005	HS
	Off	5 (13.2%)	10 (45.5%)

P-value > 0.05: Non significant; P-value < 0.05: Significant; P-value < 0.01: Highly significant

*: Chi-square test; ≠: Mann-Whitney test

LA left atrium, EF ejection fraction, CHB complete heart block, SND sinus node disease, HB heart block, RV right ventricle.

• -    Age >59 years was associated with significant AF risk p value 0.001(OR) 32.200

• -    Male Sex was associated with significant AF risk p value 0.018 (OR) 4.200

• -    Cause of implantation (SND) was associated with significant AF risk p value 0.005 (OR) 8.077

• -    Date of implantation >5 years was associated with significant AF risk p value 0.007 (OR) 9.000.

• -    RV pacing >49% was associated with significant AF risk p value <0.001 (OR) 78.750

• -    Hysteresis (off) was associated with significant AF risk p value 0.008 (OR) 5.500

• -    No IR was associated with significant AF risk p value 0.013 (OR) 4.121

• 4- Multivariate logistic regression analysis. we found that the most important variables are Age >59 p-value< 0.01Odds ratio 1187.714.Male Sex pval-ue0.003Odds ratio 42.413.No IR pvalue0.005 Odds ratio 59.351, table 10.

Pacemaker algorithms for decreasing unnecessary RV pacing

• 1 - Relation between VIP mode and RV pacing percentage

There was high significance between VIP off and RV pacing percentage P-value 0.005, table 11.

• 2 - Relation between Hysteresis and RV pacing percentage

There was high significance between hysteresis set off and RV pacing percentage P-value 0.016, table 12.

Group A follow up

• 16    Patients in group A with VIP off were changed on to the nominal values and follow up of all measurable parameters was done after 6 months. And ECG was recommended monthly or with palpitation and on follow up. Out of them 10 patients had paroxysmal AF, all of them were followed up Except one patient with persistent AF who was converted to VVIR with hysteresis this patient is lost during follow up. The nine previous patients had AHRE Burden Median (IQR) 80 (40 – 130) Range 40 – 780. After follow up the only benefit was significant decreasing RV pacing P-value 0.001.Before RV pacing (%) Median (IQR) 69 (50 – 70) range 1 – 89. And after Median (IQR) 58 (40 – 65) Range 1 – 81, table 13.

• 15    Patients in group B (10 of them had clinically ECG documented AF 2paroxysmal,3 persistent, 5 per

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Table 10

Univariate and multivariate logistic regression analysis for factors associated with AF among Group B.

	Univariate				Multivariate (Backward: Wald)
	P-value	Odds ratio (OR)	95% C.I. for OR		P-value	Odds ratio (OR)	95% C.I. for OR
			Lower	Upper			Lower	Upper
Age >59 years	0.001	32.200	3.908	265.304	0.000	1187.714	29.479	47853.155
Sex	0.018	4.200	1.285	13.731	0.003	42.413	3.452	521.097
Cause of implantation (SND)	0.005	8.077	1.888	34.552	–	–	–	–
Date of implantation >5 years	0.007	9.000	1.841	43.988	–	–	–	–
RV pacing >49%	0.000	78.750	9.152	677.649	–	–	–	–
Hysteresis (off)	0.008	5.500	1.559	19.400	–	–	–	–
No IR	0.013	4.121	1.345	12.628	0.005	59.351	3.448	1021.548

SND sinus node disease, RV right ventricle, IR intrinsic rhythm

Table 11

Relation between VIP mode and RV pacing percentage

RV pacing (%)	VIP		Test value	P-value	Sig.
	On	Off
	No. = 44	No. = 16
Median (IQR)	29 (10 - 49.5)	69 (52.5 - 74)	-2.784≠	0.005	HS
Range	0.1 – 90	1 – 89

VIP ventricular intrinsic preference, RV right ventricle

Table 12

Relation between Hysteresis and RV pacing percentage

		Hysteresis		Test value	P-value	Sig.
		On	Off
		No. = 45	No. = 15
RV pacing (%)	Median (IQR)	39 (24 - 60)	79 (31 - 89)	-2.410≠	0.016	S
	Range	1 – 90	1 – 90

RV right ventricle

Table 13

Difference between RV pacing before and after follow up group A.

		Before	After	Test value	P-value	Sig.
RV pacing (%)	Median (IQR)	69 (50 – 70)	58 (40 – 65)	-3.243≠	0.001	HS
	Range	1 – 89	1 – 81

RV right ventricleGroup B follow up menant) with hysteresis off were turned on. And follow up after 6months was done.

And ECG was recommended monthly or with palpitation and on follow up.

As regards RV pacing there was high significance for decreasing RV pacing with hysteresis on P-value 0.002.

Before RV pacing (%) Median (IQR)79 (19 – 89) Range1 – 90.

And after Median (IQR) Median (IQR) 70 (13 – 80) Range1 – 86, table 14.

There was no significant difference in decreasing AF during follow up.

Discussion

The last 2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy recommendations for pacing in patients with AV block, synco-

Table 14

Difference between RV pacing before and after follow up group B.

		Before	After	Test value	P-value	Sig.
RV pacing (%)	Median (IQR)	79 (19 – 89)	70 (13 – 80)	--3.068≠	0.002	S
	Range	1 – 90	1 – 86

RV right ventricle pe and other conduction disorders requiring pacing generally recommend dual chamber pacemakers over single chamber pacemakers except AF patients, old patients and difficult venous access.

Our study showed no significant difference between the two groups as regards AF development p value 0.071 , that was consistent with large, randomized, parallel trials that included patients with only AVB or with AVB and/or SND failed to show superiority of DDD over ventricular pacing with regard to mortality, and had not consistently shown superiority in terms of quality of life or morbidity(including stroke or transient ischaemic attack and AF) (Castella et al., 2020).

In our studty, aging was a major risk factor for AF development in the two groups in group A increased age had high significance for developing AF with P value< 0.001, that was consistent with Dębski et al. (2019) performed a study between October 4, 1984 and December 31, 2014 a total of 3932 consecutive patients underwent de novo DDD PPM implantation showed that age at implant had siginificant risk for AF developement (HR, 1.041; 95% CI, 1.033-1.049, 1-year increase) .

Also our study found significant relation between male sex and AF development in both groups ,in group A male sex was more risky than female for developing AF with significant difference and P value 0.020, which was concordant with Dębski et al. (2019) who showed that male sex was major AF risk (hazard ratio [HR], 1.316; 95% CI, 1.134-1.528, for men), .

As regards cause of implantation in Group A 3rd degree heart block had significant risk for developing AF with P value 0.047(as the patients were more dependent on pacemaker with advanced AVblock increasing the RV pacing)and also SND significant risk for developing AF with P value 0.015, in Group B as regards 3rd degree heart block had high significant risk for developing AF with p value 0.002 and also SND had high significant risk for developing AF with p value 0.002 that was inconsistent with Alonso et al., (2014) among 19,893 eligible participants (14,816 in Atherosclerosis Risk in Communities ARIC, 5077 in

CHS), 213 incident SSS events were identified and validated (117 in ARIC, 96 in CHS) during a mean follow up of 17 years rates of AF and pacemaker implantation were more than 10 and 200 times higher for those with SSS compared to those without SSS. The relationship-between AF and SSS is well-established, as attested by the co-occurrence of the two conditions in the so-called ‘‘tachy-bradysyndrome’’, the involvement of the sinoatrial node in thedevelopment of atrial tachycardias, and the presence ofdiffuse atrial remodeling in SSS patients.

Further, the risk of both SSS and AF was elevated in association with polymorphisms and mutations in the HCN4 gene, which encodes thehyperpolarization-ac-tivated ion channel HCN4, key for spontaneous pacemaker activity. Alonso et al., (2014)

As regard the pacing parameters optimizing the modes and algorithms in every patient has a pivotal role in decreasing the AF risk. The main technique was preventing unnecessary Ventricular Pacing. As mentioned in ESC 2021Unnecessary RV pacing should be systematically avoided in patients with SND, because it may cause AF and deterioration of HF, particularly if systolic function is impaired or borderline (Sweeney et al., 2007).

A lot of Algorithms had been established for that like minimal ventricular pacing, managed ventricular, VIP pacing VVIR with rate hysteresis.

As regards ventricular pacing percentage in our study there was very strong relation between it and AF in the two groups so the main aim in our study was finding the relation between unnecessary ventricular pacing by VIP mode in group A and Hysteresis in group B and AF development un surprisingly patients without VIP mode had increased risk of unnecessary ventricular pacing there was high significance between VIP off and RV pacing percentage P-value 0.005 and with VIP mode OFF there was high significance of developing AF with P value <0.001.

As regards RV pacing percentage in Group A increasing that value had high significance for developing AF with Median (IQR70 (69 – 89) Range 50 – 90P

Issue 23. August 2022 | Cardiometry | 73

<0.001, in Group B RV pacing (%) Median (IQR) 79 (69 – 89) had high significant risk for developing AF with p value< 0.001 that was consistent with Veasey et al. (2011)a study with Sixty-six patients were randomized to receive either conventional dual chamber pacing (DDDR, n =33), or dual chamber minimal ventricular pacing (MinVP, n = 33) At follow-up, the device-derived AF was significantly lower in the Min-VP cohort when compared with the DDDR cohort (12.8+15.3% vs. DDDR 47.6+42.2%, P = 0.001). Kaplan–Meier estimates of time to onset of persistent AF showed significant reductions in the rates of persistent AF for MinVP pacing (9%) when compared with conventional DDDR pacing (42%), P =0.004.

Also Yadav et al. (2015)in a study with Seventy-one patients completed the 12 month follow-up period showed that Activating VIP resulted in a significant reduction of RV pacing after 12 months in both the compromised AV conduction and intact AV Conduction arms VIP reduced the %RVp from 68 - + 39% in the CG to 15 - + 25% in the TG (p=0.0067). In the cAVC arm, VIP reduced the % RVp from 97 - + 3% in the CG to 39 - + 41% in TG (p¼0.0004).

In Group A as regards Atrial pacing percentage Median (IQR) 19 (15 – 27.1) Range 11 – 62 there was high significance of developing AF with P value <0.001 this may be explained partly by the phenomena of competitive atrial pacing and was consistent with Wass et al. (2020) study with Among 23 patients identified as having episodes of CAP, 22 had St Jude Medical (Abbott) pacemakers or implantablecardioverter defibrillators (ICDs) and one had a Boston Scientific Corporation ICD. CAP triggered AF in 12 patients (52%). Examples was shown in Duration of CAP-induced AF ranged from 10 seconds to 28 hours 32 minutes. Four of the 12 patients (33.33%) with CAP induced AF were not on any anticoagulation at the time of CAP detection; their CHA2DS2-VASc scores ranged from 1 to 7 with a mean of 4.

Electrograms from all patients were available for review. In the patients with St Jude Medical/Abbott devices, and it was noted in 20 of 22 patients that CAP occurred during sensor-indicated rate (SIR) pacing. This was not limited to high atrial rates but also present at relatively slower rates as well. In one patient with a Boston Scientific Corporation device, electrograms were also consistent with sensor-indicated pacing given the rate of atrial pacing was higher than the programmed base rate.

As regards hysteresis in the group B for minimization of the RV pacing there was high significance between hysteresis off and RV pacing percentage P-value 0.016 and high risk for AF development p value 0.005.

Also patient having no IR in the two groups during interrogation had significant risk of AF as it may be an indicator of pacemaker dependence with increased RV pacing percentage.

Also date of PM implantation had significant AF risk in the two groups and was an indicator of increased RV pacing also.

As regards AHRE in our dual chamber group it increased the risk of AF, AHRE duration had high significant risk for AF development Median (IQR) 70 (50 - 130) minutes P value 0.001, that was consistent with Doundoulakis et al. (2021) study which showed that the overall AHRE incidence ratio was estimated to be 17.56 (95% CI, 8.61 to 35.79) cases per 100 person-years, Evidence of moderate certainty suggests that patients with documented AHREs were 4.45 times (95% CI 2.87–6.91) more likely to develop clinical AF.

The results of our study (group A) as regards the non significant role in apical versus septal lead position as a risk for AF development p value 0.058 were in agreement with Dębski et al. (2019). During the follow up period in group A VIP on there was high significance in drcreasing RV pacing P-value 0.001 that is consistent with Yadav et al. (2015) as mentioned before and no effect on AF risk mostly due to the short duration of the follow up.

Also turninig hysteresis on there was high significance in drcreasing RV pacing P-value 0.002.

Conclusion

There is no significant difference between the two groups in AF development.

And the risk of AF increases with RV pacing in the two groups,also the date of implantation, CHB and SND are major risk factors in the two groups.

In group A VIP off increases the risk and AHRE duration especially subclinical AF also increases the risk.

In group B(control group) hysteresis off increases the risk.

So the goal after pacemaker implantation is optimizing the algorithms for every patients specially in patients having some intrinsic rhythms every efforts should be made to minimize RV and atrial pacing.

Limitations

Small sample size-Limited duration of the follow up.

Financial support and sponsorship

Nil

Conflicts of interest

There are no conflicts of interest.