Single versus Dual-Chamber Pacing in a Sub-Saharan African Heart Center: Characteristics and Prognosis

Anicet Kassi Adoubi^1*, Florent Diby², Pinnin Ouattara², Ambroise Gnaba², Flavien Kendja³

¹Abidjan Heart Center, Université Alassane Ouattara, Bouaké, Côte d'Ivoire

²Université Alassane Ouattara, Bouaké, Côte d'Ivoire

³Abidjan Heart Center, Université Félix Houphouet Boigny, Abidjan, Côte d'ivoire

^*Corresponding author: Anicet Kassi Adoubi, Abidjan Heart Center, Université Alassane Ouattara, Abidjan, Bouaké, Côte d'Ivoire

Received: 20 December 2020; Accepted: 04 January 2021; Published: 20 January 2021

1. Introduction

In sub-Saharan Africa, pacemaker therapy is still in the embryonic stage [1, 2]. A Pan-African Society of Cardiology (PASCAR) survey about 31 African countries reported that 30% of African countries had limited access to pacemaker insertion [3]. Eight of the 31 countries surveyed (26%) did not have access to pacemaker implantation. So, this practice is limited by insufficient technical, human resources, and patients' incomes. Thus, the dual-chamber pacemaker may appear to be significantly much more expensive than the single-chamber pacemaker. So in practice, we often suggest that patients choose the pacing mode according to their financial capabilities. Randomized studies from the early 2000s had compared dual-chamber (atrioventricular) and single chamber (ventricular) pacing mode [4-6]. Although the dual-chamber pacing had appeared to be more beneficial in terms of quality of life, this mode had not demonstrated superiority in morbidity and mortality. Current guidelines do not exclude the choice of single-ventricular pacing, particularly in cases of atrioventricular block [7, 8]. But several experts have found these results questionable [9, 10]. In practice, the use of single-ventricular pacemakers in developed countries has significantly decreased in favor of dual-chamber pacemakers [11, 12]. Besides, numerous cardiac pacing concepts and pacemaker technology have evolved [13, 14]. In this context, this work sought to compare our patients' characteristics and prognosis with single-chamber ventricular pacing with those with dual-chamber pacing.

2. Patients and Methods

2.1 Selection

We conducted a non-randomized retrospective cohort study of patients implanted with pacemakers between 2006 and 2016 at Abidjan Heart Center in Ivory Coast. Patients included in our study had a typical indication for cardiac pacing (bradycardia). For this reason, we inserted a single or a dual-chamber pacemaker according to the underlying disease and financial capabilities of patients. We excluded for this study all patients who received an implantable cardiac defibrillator, a pacemaker for cardiac resynchronisation therapy, had the right ventricular lead positioned outside the apex, or have had a cardiac surgery three months before or in the years following the pacemaker's implantation.

2.2 Analyzed parameters

At the time of the first pacemaker implantation, we systematically recorded

• demographic data (sex and age at pacemaker implantation),
• patient history ( hypertension, diabetes),
• functional and clinical signs (syncope, pre-syncope, palpitations, dizziness, asthenia, confusion, NYHA stage),
• echocardiographic findings (structural heart disease or not, left ventricular ejection fraction),
• indications for cardiac pacing (atrioventricular block, sick sinus syndrome, atrial fibrillation),
• type of pacemaker implanted,
• and the medications at discharge (use of ACE inhibitors, Angiotensin 2 receptors blockers, diuretics, beta-blockers, nitrates, calcium channel blockers, digoxin, amiodarone, vitamin K antagonist, aldosterone antagonist).

After discharge, patients had a visit the first month, the third month, and then every six months. At the third month, we recorded the NYHA stage, early complications (i.e., those that occurred before three months), pacemakers parameters, and possible pacemaker dependency. The deadline for follow-up was December 31, 2017.We obtained data on late complications (those that occurred after the follow-up at three months), rehospitalizations, and deaths. If these data were not available in patients' files, we collected these data by telephone from the patients (with their prior agreement) or their referring physicians. We defined partial pacemaker dependency in patients with sinus dysfunction whose percentage of atrial stimulation was above 80% at a frequency programmed at a minimum frequency of 60 bpm and in patients with an atrioventricular block if the rate of ventricular stimulation was above 80% programmed at a minimum frequency of 60 bpm. Total pacemaker dependency was defined if, in addition to partial pacemaker dependency, spontaneous activity was absent at single atrial-chamber pacing (AAI) at 30 bpm (in sinus dysfunction) or single-ventricular chamber pacing (VVI) 30 bpm (in atrioventricular block) for 30 seconds.

2.3 Clinical endpoint

Because of the lack of possibility to determine the exact cause of death of most patients on the data obtained, death for all-cause was established as the endpoint.

2.4 Statistical analysis

We presented the characteristics of the study population and the cardiac pacing using descriptive statistics. We carried out the comparisons between the groups for the descriptive variables with the chi-square test, and, if not possible, Fisher's exact test for the categorical variables. The continuous variables were compared using the Student's t-test or the Mann-Whitney U test, according to their characteristics. A univariate Cox proportional hazards model was used to identify the independent predictors of all-cause death from the variables usually known as such. Variables with a p-value < 0.05 were included in the multivariable Cox model. The final models for predicting each study outcome were determined using all the variables from the initial model. The bootstrap method with 1000 iterations was used to validate the final model. The cumulative incidence of deaths was generated using the Kaplan-Meier method and compared using the log-rank test between the two groups studied and according to the type of pacemaker (single versus dual-chamber pacemaker). All the analysis were done in intention-to-treat. A value of p < 0.05 was considered statistically significant. The data were analyzed using SPSS software version 23.

2.5 Ethical considerations

The Abidjan Heart Institute ethics committee approved the study. The data collected were analyzed under the data protection laws for individuals, following ethical principles according to the Declaration of Helsinki.

3. Results

3.1 Patients' characteristics

During the period, among 325 patients implanted, 283 patients met the selection criteria. The patients' mean age was 67.3 ± 12.6 years; 49.1% were male (Table1). The main symptoms were syncope (38.5%) and dizziness (30.5%). Eighty-five patients (30%) had underlying heart disease. The primary indication for pacing was a complete atrioventricular (AV) block (83.3%). One hundred and eighty-nine patients (66.8%) received a single chamber ventricular pacemaker, and 94 (33.2%) a dual-chamber pacemaker. After implantation, 16 patients (5.7%) experienced early complications and 15 (5.3%) late complications (Table 2). After discharge, 257 patients (91.2%) had their pacemaker checked at three months. Six patients died before three months, and 20 others were not present at the visit on this date. The tests revealed frequent pacemaker dependency (76%).

3.2 Comparison of patients with single versus dual-chamber pacemaker (Table 1 & 2)

These two groups of patients were comparable concerning gender, comorbidities, underlying heart disease, and left ventricular ejection fraction (Table 1). But the patients with single-chamber pacemakers were significantly older (68.7 ± 11.2 vs 64 ± 14.8, p = 0.02), and more often had syncope (43.3% vs 28.7, p = 0.017). Single-chamber ventricular pacing was prescribed more often in patients with atrioventricular block (86.2 vs76.2, p = 0.042) and much less often in sinus dysfunction (1.1% vs 17%, p <0.001). Postoperatively, the complications were comparable in the two groups, as were the readmissions (Table 2). At 3 months, we observed a stronger dependency of patients with single-chamber pacemakers (34.9% vs 19.3%, p = 0.009) and a higher percentage of ventricular pacing (90.4 ± 19% vs 84.4 ± 28.1%, p = 0.043). During follow-up period, three patients with single-ventricular pacemaker experienced severe pacemaker syndrome. We upgraded their pacemaker to dual-chamber. Two patients with a dual-chamber pacemaker with atrial lead dislodgement had their pacemakers reprogrammed in single-ventricular pacing mode. We did the same procedure for two patients who had a permanent atrial fibrillation one year after dual-chamber pacemaker implantation.

3.3 Patients' prognosis (Table 3)

At the end of the follow-up period (median : 3.67 years, IQ [2.07;6.10], 73 patients (25.8%) was dead. In univariate analysis, according to the Cox model, the risk factors for death in our retrospective cohort were age, the presence of heart failure on admission, a left ventricular ejection fraction <0.40, syncope, the presence of atrial fibrillation, the occurrence of complications and the insertion of a single-chamber pacemaker (RR =1.974; 95% CI [1.132,3.44], p = 0.017) In multivariate analysis, only age was a factor of poor prognosis (RR = 1.027 95% CI [1.005,1.050], p = 0.017). The Kaplan-Meier curve and the Log-Rank test confirmed the prognostic role of the type of pacemaker (Log Rank = 5.97, p = 0.015) (Figure 1). But in the subgroups of patients with an atrioventricular block (without atrial fibrillation) (Figure 2) and in that of subjects under 80 years of age (Figure 3), this prognostic role was not confirmed (respectively p = 0.052 and p = 0.067).

Characteristics	Overall N=283	VVI (N=189)	DDD (N=94)	p-value
Demographic
Male (%)	139 (49.1)	89 (47.1)	50 (53.2)	0.33
Age (years)	67.3 ± 12.6	68.7± 11.2	64 ± 14.8	0.02
Symptoms
Syncopes (%)	109 (38.5)	82 (43.3)	27 (28.7)	0.017
Presyncope (%)	42 (14.8)	30 (15.9)	12 (12.8)	0.49
Dizziness (%)	86 (30.5)	56 (29.6)	30 (31.9)	0.69
Asthenia (%)	22 (7.8)	10 (5.3)	12 (12.8)	0.027
Confusion	12 (4.2)	11 (5.8)	1 (1,1)	0.068
NYHA at admission
I	179 (63.3)	122 (64.9)	57 (60.6)	0.79
II	21 (7.4)	15 (7.9)	6 (6.4)
III	74 (26.1)	46 (24.3)	28 (29.8)
IV	9 (3.2)	6 (3.2)	3 (3.2)
Comorbidities
Hypertension (%)	211 (74.6)	140 (74.1)	71 (75.5)	0.79
Diabetes (%)	45 (15.9)	29 (15.3)	16 (17)	0.71
Heart failure	68 (24)	44 (23.3)	24 (25.5)	0.68
Main echocardiography findings
DCM (%)	37 (13.1)	22 (11.6)	15 (16)	0.35
ICM (%)	10 (3.5)	7 (3.7)	3 (3.2)	0.56
LVH	29 (10.2)	20 (10.6)	9 (9.6)	0.49
Normal heart (%)	198 (70)	137 (72.5)	61 (64.9)	0.12
Others (%)
LVEF	0.61 ± 0.11	0.61 ± 0.11	0.60 ±0.12	0.56
LVEF<40% (%)	20 (7.1)	11 (5.8%)	9 (9.6)	0.25
Indications
AVB (%)	235 (83)	163 (86.2)	72 (76.2)	0.042
SND (%)	18 (6.4)	2 (1.1)	16 (17)	<0.001
AF (%)	30 (10.6)	24 (12.7)	6 (6.4)	0.10
Mode of Stimulation
VVI (%)	189 (66.8)
DDD (%)	94 (33.2)
Length of stay at Hospital (days)	6 (4-8)	6 (4-8)	5 (4-7)	0.07
Rehopitalization	58 (20.5)	41 (21.7)	21 (18.1)	0.48
Heart failure de novo	12 (4,2)	7 (3.7)	5(5.3)	0.54
Temporary pacing (%)	184 (65)	137 (72.5)	47 (50)	<0.0001
Medication at discharge
ACEI /ARB	183 (64.7	124 (65.6)	59 (62.8)	0.64
Diuretics	162 (57.2)	108 (57.1)	54 (57.4)	0.96
Betablockers	21 (7.4)	8 (4.2)	13 (14)	0.003
Aldosteron Antagonist	29 (10.2)	14 (7.4)	15 (16)	0.025
Digoxin	15 (5.3)	12 (6.3)	4 (4.3)	0.47
Nitrates	32 (11.3)	22 (11.6)	11 (11.7)	0.99
Calcium channel blockers	81 (29.4))	54 (28.7)	29 (30.9)	0.71
Amiodarone	15 (5.3)	9 (4.8)	6 (6.4)	0.56
Aspirin	49 (17.3)	31 (16.4)	18 (19.1)	0.57
Vitamin K antagonist	17 (6)	12 (6.3)	4 (5.3)	0.73
NYHA: New York Heart Association, DCM: Dilated cardiomyopathy, ICM: ischemic cardiomyopathy, LVEF: Left Ventricular Ejection Fraction, LVH: Left ventricular hypertrophy, AVB= atrioventricular block, SND: sinus node dysfunction, AF: Atrial Fibrillation. ACEI/ARB: angiotensin conversion enzyme inhibitors/ angiotensin 2 receptor blockers.

Table 1: Baseline characteristics of all patients and comparison between patients with a single-ventricular pacemaker (VVI) and a dual-chamber pacemaker (DDD).

Characteristics	Overall N=283	VVI N= 169	DDD N= 88	P
Pacemaker parameters at three months	N = 257
A pacing threshold, V	0.5 (0.5-0.7)	/	0.5 (0.5-0.7)	/
Sensed P voltage, mV	3.1 (2.25 – 4.95)	/	3.1 (2.25 – 4.95)
A lead impedance, ohm	347.7 ± 121.3	/	347.7 ± 121.3	/
V pacing threshold, V	0.93 ± 3.2	0.72 ± 0.72	1,33 ± 5.33	0.15
Sensed QRS voltage, mV	10.5 ± 5	9.9 ± 4.3	10.5 ± 5	0.06
V lead impedance, ohm	403.5 ± 93.2	413.3 ± 102.3	384.5 ± 69.6	0.018
Cumulative A pacing, %	31.24 ± 33.4	/	31.24 ± 33.4	/
Cumulative V pacing, %	88.4 ± 22.7	90.4 ± 19	84.4 ± 28.1	0.043
Complete pacemaker Dependency (n= 257)	76 (26.9)	39 (34.9)	17 (19.3)	0.009
Partial pacemaker Dependency (n= 257)	215 (83.7)	145 (85.8)	70 (79.5)	0.2
NYHA at 3 months (n = 257)
I.	216 (84))	140 (82.8)	76 (86.4)	0.11
II	29 (10.9)	17 (10.1)	11(12.5)
III	13 (5.1)	12 (7.1)	1 (7.7)
Early complications	16 (5.7)	7 (4.1)	8 (9.1)	0.11
Late complications (%)	15 (5.3)	8 (4.7)	6 (6.8)	0.48
Rehospitalisation	58 (20.5)	41 (21.7)	21 (18.1)	0.48

Table 2: Data on the patients’ follow-up. Comparison between patients with a single-ventricular pacemaker (VVI) and a dual-chamber pacemaker (DDD).

Variables	Univariate analysis					Multivariate analysis
	p-value	HR	95% CI			p-value	HR	95% CI
			Lower	Upper				Lower	Upper
Age	0.005	1.030	1.009		1.052	0.017	1.027	1.005	1.050
Hypertension	0.999	1.000	0.580		1.723
Diabete	0.703	1.125	0.616		2.054
Temporary pacing	0.135	.821	.633		1.063
VVI ± R pacing	0.017	1.974	1.132		3.441	0.07	0.588	0.333	1.040
Complications	0.005	2.39	1.31		4.36	0.103	1.720	0.895	3.305
Atrial Fibrillation	<0.001	3.694	2.102		6.492	0.015	2.181	1.162	4.092
AVB	0.001	0.432	0.257		0.725
Syncopes	0.014	1.797	1.128		2.861	0.145	1.439	0.882	3.241
Heart failure	0.002	2.139	1.335		3.428	0.185	1.444	0.839	2.487
LVEF < 0.40	<0.001	3.671	1.968		6.846	0.093	1.925	0.897	4.131
NYHA: New York Heart Association, LVEF: Left Ventricular Ejection Fraction, SND: Sinus Node Disease, AVB: AtrioVentricular Block.

Table 3: Univariate and Multivariate analysis of prognostic factors of death.



Figure 1: Kaplan-Meier survival curves for the patients with implanted Single-ventricular pacemakers (VVI) versus dual-chamber pacemakers (DDD) over a 10-year follow-up period. Means survival time VVI = 7.95 ± 0.39 years vs DDD = 8.49 ± 0.308 years.



Figure 2: Kaplan-Meier survival curves for the patients in atrioventricular block implanted with single-ventricular pacemakers (VVI) versus dual-chamber pacemakers (DDD) over a 10-year follow-up period. Means survival time VVI = 8.44 ± 0.40 years vs DDD = 8.76 ± 0.41 years.



Figure 3: Kaplan-Meier survival curves for the patients under 80 years with implanted single-ventricular pacemakers (VVI) versus dual-chamber pacemakers (DDD) over a 10-year follow-up period. Means survival time VVI = 8.10 ± 0.41 years vs DDD = 8.36 ± 0.42 years.

4. Discussion

In our cohort of patients from sub-Saharan Africa, patients with single-chamber pacing had a more severe prognosis than patients with dual-chamber pacing. But this higher mortality was linked to older age and a more significant presence of atrial fibrillation in this group. The characteristics of patients receiving cardiac stimulation in sub-Saharan Africa differ from those in developed countries: they are much fewer, younger, and have a more severe clinical status [1, 15, 16]. Indeed, there is insufficient infrastructure and a lack of specialists practicing pacemaker therapy [2, 17]. It doesn't even exist in some countries. Besides, the cost appears excessive for the populations [2]. So much so that, among the patients who indicate cardiac pacing, very few benefit from it. These are generally the youngest patients (still in activity, therefore able to cover the pacemaker's cost) and the most serious (those who have frequent syncopes or pre-syncopes). In our cohort, we have a large number of patients who had syncopes or pre-syncopes (53.3%), a large number of patients with pacemaker dependency, and very few presenting with sinus node dysfunction.

In our context, patients prefer single-ventricular pacemakers because of their lowest cost. Although being the third choice in an atrioventricular block, it is easier to implant in the ESC guidelines and is associated with fewer complications than the DDD pacemaker [8, 18]. In our work, we have twice more difficulties with DDD, but this difference is not significant. But in 2020, the advantages of the dual-chamber pacemaker are indisputable [19]: it avoids the pacemaker syndrome, which may require reoperation. It allows, with its memories, to diagnose with precision paroxysmal ventricular and supraventricular arrhythmias. It avoids the unnecessary pacing of the right ventricle, which can be deleterious in certain situations with the news algorithm for preserving ventricular pacing. It decreases the risk of atrial fibrillation [4-6]. When we compare the two groups of patients, we realize that the single-chamber pacemaker was (unintentionally) chosen for the most severe cases: older subjects with a greater syncope and atrial fibrillation frequency. These three characteristics may explain the higher mortality in this group.

Older subjects naturally have a poorer prognosis than younger subjects. They also have a more significant number of comorbidities. Finally, the dual-chamber pacing would be more beneficial for them in this area. In a study of 140 patients over 80 years of age followed for four years after implantation of pacemakers, the prognosis was significantly favorable in the group of patients with dual versus single-chamber pacing (20). In a randomized, double-blind study with double cross-over, Ouali et al. analyzed patients' clinical status over 70 years of age stimulated for atrioventricular block [21]. They showed that patients in single-chamber with rate response (VVIR mode) had a lower quality of life than dual-chamber pacing. Also, they experienced impaired left ventricular function, left atrium enlargement, and degradation of their functional capacity. These changes can lead to heart failure more quickly and then to death. Syncope is usually a clinical manifestation that unequivocally indicates pacemaker implantation for patients with proven or suspected severe bradycardia. But another aetiology cannot be ruled out if the mechanism of syncope is not documented. Ricci et al.'s meta-analysis showed that among older, diabetic, and/or hypertensive individuals, a history of noncardiac/unexplained syncopes, even in the absence of an obvious cardiac etiology, is associated with higher all-cause mortality [22]. Atrial fibrillation is relatively common in the elderly and among patients with pacemakers [23]. Single-ventricular pacing, in that case, favors its occurrence [4]. Atrial fibrillation increases the risk of death by two in women and by 1.5 in men [25, 26]. 20 to 30% of strokes are due to this condition [27]. And we find 20 to 30% of left ventricular dysfunction among patients with atrial fibrillation [28]. The single ventricular- pacing mode (with rate response) is recommended for patients with permanent atrial fibrillation [7, 8]. All these facts combined may explain that, in our cohort, atrial fibrillation is a predictor of death and associated with single-ventricular pacing.

4.1 Limitations

This work was a retrospective, non-randomized study. So, some data could not be obtained. Left ventricular ejection fraction was not assessed, after pacemaker implantation, during the follow-up. QRS duration and type were not taken into account and could help to understand patients' outcomes. Switches from dual-chamber mode to single ventricular mode and vice-versa were not considered. But despite these shortcomings, our study had the advantage of being carried out in real life and giving results consistent with the randomized studies.

5. Conclusion

This study allows us to consider changes to our practices even though our resources are limited. Thus, we need to reconsider the dual-chamber pacing in the elderly. Besides, we should use the methods of preservation of right ventricular pacing to avoid the occurrence of de novo atrial fibrillation. If the left ventricular ejection fraction is impaired, it would be helpful to avoid pacing in the apex of the right ventricle; It would be better to perform His or left bundle branch pacing.

Ethics Statement

The Abidjan Heart Institute ethics committee approved the study. The data collected were analyzed under the data protection laws for individuals, following ethical principles according to the Declaration of Helsinki.

Acknowledgements

The authors express their gratitude to the staff of the pacing unit of Abidjan Heart Institute.

Conflicts of Interest

None declared. All the authors express that there was no conflict of interest in writing this research article

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