Mid-Range Paced-QRS as an Independent Negative Predictor of Cardiac Events　― Right Ventricular Pacing Implications ―

Abstract

Background: The effect of paced-QRS (p-QRS) duration on long-term outcomes is unclear, so we assessed the association between p-QRS duration and cardiac events.

Methods and Results: We enrolled 187 patients (103 males, mean age: 77±12 years) who underwent pacemaker implantation between 2018 and 2021. During the median follow-up period of 972 days (761–1,292 days), 18 patients experienced cardiac events (1 cardiac death, 17 heart failure hospitalizations). The p-QRS duration was longer in the cardiac event group than in the noncardiac event group (162±17 vs. 148±17 ms, P=0.005). Receiver operating characteristic curve analysis identified 149 ms as the optimal cutoff value for predicting cardiac events (area under the curve, 0.72). Kaplan-Meier analysis showed better outcomes for mid-range p-QRS duration (≤149 ms, n=89) compared with long p-QRS duration (>149 ms, n=98) (P=0.005). Multivariate Cox hazard analysis indicated a good outcome with mid-range p-QRS duration (hazard ratio: 0.28, 95% confidence interval: 0.06–0.88, P=0.029).

Conclusions: A p-QRS duration of ≤149 ms was associated with a reduction in cardiac events. Therefore, it may serve as a target index of success in right ventricular pacing.

Pacemaker implantation is an effective therapy for patients with symptomatic bradyarrhythmia.^1–4 Although several positions have been devised as right ventricular (RV) pacing sites, pacemaker-induced cardiomyopathy could be evident in up to 9% of patients with RV pacing.⁵ A previous study reported that RV pacing increases the rate of heart failure (HF) compared with the intrinsic conduction beat.⁶ Several studies have demonstrated the relationship between HF and the pacing anatomical site, pacing burden, and paced-QRS (p-QRS) duration.^7–9 A longer p-QRS duration leads to left ventricular (LV) desynchrony and hospitalization for patients with HF. We previously reported that a short p-QRS duration (<132 ms), attributed to retrograde penetration pacing into the conduction system via RV septal pacing, was associated with a high frequency of LV synchrony and maintained postoperative cardiac function.¹⁰ Conversely, large randomized controlled trials found no protective effect of RV septal pacing on RV apex pacing. Therefore, the best pacing conditions, especially regarding long-term outcomes, remain unclear.¹¹

Hence, in this study, we aimed to assess the association between p-QRS duration and long-term outcomes.

Methods

Study Population and Protocol

This retrospective single-center study included all consecutive patients who underwent de novo pacemaker implantation with transvenous leads between September 1, 2018, and April 31, 2021. The following patients were excluded from this analysis: (1) patients with RV pacing ratio <40%, and (2) those without ECG data pertaining to RV pacing. The study patients were classified into cardiac and noncardiac event groups. The rates of cardiac death and hospitalization for HF were evaluated as cardiac events. Cardiac death was defined as death due to HF, ventricular arrhythmia, or LV-assist device implantation. Hospitalization for HF was defined as sudden or gradual onset of symptoms based on the New York Heart Association functional class III or IV HF requiring unplanned hospitalization. We determined the required p-QRS duration to assess the possibility of cardiac events using receiver operating characteristic curve analysis. We also compared the association between the p-QRS duration and cardiac events.

Ethics Declaration

This study was conducted in accordance with the principles outlined in the Declaration of Helsinki and was approved by the institutional ethics committee (National Cerebral and Cardiovascular Center M26-150). This was a retrospective study that analyzed anonymous data generated after patients agreed to undergo treatment; hence, an opt-out method was used to obtain informed consent.

Pacemaker Implantation

Fluoroscopically guided transvenous lead placement was performed via the subclavian vein. The right atrial leads were positioned at the right auricular appendage or right atrial septum. The position of lead implantation in the RV was decided by the operator. In almost all patients who underwent RV septal pacing, the RV lead (SelectSecure lead 3830-69; Medtronic, Minneapolis, MN, USA) was positioned using a catheter delivery system (C315 delivery catheter, C315HIS; Medtronic). In patients with RV apex pacing, RV leads were positioned using a standard technique for stylet or catheter delivery systems (C315 delivery catheter, C315S10; Medtronic). All RV leads were positioned using fluoroscopy, and RV lead position was evaluated with reference to the “9-partition method”.¹² Subsequently, the septal orientation was ensured using the left anterior oblique view. The septal pacing was categorized into the basal (tricuspid valve side and mid-level areas of the “9-partition method”) and mid (central areas) septal sites. Furthermore, the apical pacing was defined mainly as the pacing of apical side and low-level areas.

Pre- and Postoperative Cardiac Examinations

Data pertaining to baseline ECG parameters were acquired from results obtained close to the implantation period. Postoperative ECG was performed approximately 1 month after pacemaker implantation or at the point where stable RV pacing was confirmed. Based on the RV pacing waveform, a pacing waveform utilizing the native conduction system was selected. We have previously defined this waveform.¹⁰ Briefly, the waveform is composed of 2 components (a wide (W) component in the early phase, and a narrow (N) component in the late phase), and a WN waveform is observed in at least 2 leads (Supplementary Figure). Pacemaker data, including RV pacing ratio, were acquired for 6–12 months or during monthly remote monitoring. All echocardiographic data were obtained from 3 consecutive cardiac cycles. The LV ejection fraction (LVEF) was measured using Simpson’s biplane method.

Statistical AnalysIs

Data were analyzed using the JMP software (version 11.2.01, SAS Institute, Cary, NC, USA). Continuous variables are expressed as mean±standard deviation and were compared using Student’s t-test. Categorical variables were compared using Fisher’s exact test. The cumulative incidence and event-free curves were based on the results of the Kaplan–Meier analyses, stratified by study group, and compared using the log-rank test. The hazard ratios are reported with their 95% confidence intervals. To identify the independent predictors of clinical response, univariate analyses were first performed, and the predictors with a significance level <5% were included in the multivariable models. Multivariate analyses were performed using the Cox regression models. Statistical significance was set at P<0.05.

Results

Patients’ Characteristics

Among the 408 consecutive patients who underwent pacemaker implantation with transvenous leads between September 2018 and April 2021, we evaluated 187 with RV pacing ratios >40% (Figure 1). The patients’ mean age was 77±12 years, and 103 patients (55%) were male. Baseline patient characteristics are shown in Table 1. A total of 37 patients (20%) had ischemic cardiomyopathy, and the mean LVEF was 60±7%. The mean pre-QRS and p-QRS durations were 123±27 ms and 150±17 ms, respectively, and the RV pacing ratio was 93±14%. Among the 118 patients with RV septal pacing, the RV leads were positioned using catheter delivery (C315 delivery catheter, C315HIS; Medtronic) in 105 (95%) patients. On the other hand, among the 69 patients with RV apical pacing, the RV leads were positioned using catheter delivery systems (C315 delivery catheter, C315HIS; Medtronic) in 5 (5%) patients. When septal pacing was performed, the apical and tricuspid valve sides of the basal and mid-septal areas, respectively, were mainly selected as pacing sites. In this study, no significant difference was found in p-QRS duration between immediately after the pacemaker implantation and the follow-up period (150±17 vs. 152±18 ms, P=0.144).

Figure 1.

Overview of the study population. Among the 408 consecutive patients who underwent pacemaker implantation during the study period, we evaluated 187 with a ventricular pacing ratio ≥40% and ECG recordings in whom p-QRS waveform could be analyzed. HF, heart failure; PM, pacemaker; p-QRS, paced QRS; RV, right ventricle.

Table 1.

Baseline Characteristics of Patients With and Without Cardiac Events

	All patients (n=187)	Cardiac events (n=18)	Noncardiac events (n=169)	P value
Age, years	77±12	78±11	77±13	0.686
Men	103 (55%)	10 (56%)	93 (55%)	>0.999
Height, cm	159±10	158±10	159±10	0.763
Body weight, kg	57±12	56±12	57±12	0.776
Indication for implant (%)
SSS/AV block	21/166	6/12	15/154	0.008
AV block	141 (75%)	9 (50%)	132 (78%)	0.999
Atrial fibrillation	57 (30%)	10 (56%)	47 (29%)	0.028
ICM	37 (20%)	3 (17%)	34 (52%)	>0.999
Medical history of HF	19 (10%)	4 (22%)	15 (9%)	0.092
HT	100 (54%)	10 (59%)	90 (53%)	0.800
DM	42 (23%)	6 (35%)	36 (21%)	0.223
LVEF, %	60±7	57±9	60±7	0.129
LVDd, mL	48±6	51±7	47±6	0.042
LVDs	31±6	35±6	31±6	0.016
IVST	9±2	9±2	9±2	0.479
PWT	9±2	10±2	9±2	0.253
Pre-QRS, ms	123±27	132±30	122±27	0.158

Data are expressed as mean±standard deviation or number (percentage). AV, atrioventricular; DM, diabetes mellitus; HF, heart failure; HT, hypertension; ICM, ischemic cardiomyopathy; IVST, interventricular septum thickness; LVDd, left ventricular end-diastolic diameter; LVDs, left ventricular end-systolic diameter; LVEF, left ventricular ejection fraction; PWT, posterior left ventricular wall thickness; SSS, sick sinus syndrome.

Clinical Outcomes of RV Pacing

During a median follow-up period of 972 days (interquartile range, 761–1,292 days), 1 patient experienced cardiac death, whereas 17 patients were admitted to the hospital due to HF. Patients with atrial fibrillation before pacemaker implantation were significantly more frequent in the cardiac event group than in the noncardiac event group. LV end-diastolic diameter and LV end-systolic diameter were wider in the cardiac event group than in the noncardiac event group. No significant differences were observed in the pre-QRS duration or EF between the 2 groups. With respect to the pacing parameters, the RV lead position (septal or apex), V pacing burden, and use of the catheter delivery system were comparable between groups. When the RV lead positions were examined in detail, patients with basal septal pacing had no cardiac events, and all cardiac events occurred in those with mid-septal and apical pacings. The p-QRS duration was longer in the cardiac event group than in the noncardiac event group (Table 2) (162±17 vs. 148±17 ms, P=0.005). Receiver operating characteristic curve analysis revealed that the optimal cutoff value for the p-QRS duration was 149 ms for the prediction of cardiac events (area under the curve, 0.72; sensitivity, 89%; specificity, 52%; positive predictive value, 16%; and negative predictive value, 98%). Kaplan-Meier analysis revealed that the mid-range p-QRS duration group (≤149 ms, n=89) had a better outcome (i.e., cardiac death and HF-related hospitalization) than the long p-QRS duration group did (>149 ms, n=98; log-rank P=0.007; Figure 2), and the multivariate Cox hazard analysis showed that a mid-range p-QRS duration was associated with a good outcome (hazard ratio: 0.24, 95% confidence interval: 0.05–0.77, P=0.015; Table 3). Three patients had p-QRS ≤149 ms and subsequent heart failure hospitalization (Supplementary Table). Among the 92 patients with echocardiographic follow-up data, LVEF during the follow-up period was significantly low in the those with cardiac events (47±15% vs. 59±7%, P=0.013).

Table 2.

Pacing Parameters

	All patients (n=187)	Cardiac events (n=18)	Noncardiac events (n=169)	P value
RV septal pacing	118 (63%)	8 (44%)	110 (65%)	0.121
V pacing ratio, %	93±14	88±18	93±14	0.259
p-QRS, ms	150±17	162±17	148±17	0.005
AF after PMI	117 (63%)	14 (78%)	103 (61%)	0.205
WN component	77 (41%)	4 (22%)	73 (43%)	0.129
CDS	110 (59%)	8 (44%)	102 (60%)	0.215

Data are expressed as mean±standard deviation or number (percentage). AF, atrial fibrillation; CDS, catheter delivery system; PMI, pacemaker implantation; p-QRS, paced QRS; RV, right ventricle; WN, wide narrow.

Figure 2.

Kaplan-Meier analysis demonstrated that patients with p-QRS duration ≤149 ms had a better outcome (i.e., cardiac death and heart failure hospitalization rates) than patients with p-QRS duration >149 ms (log-rank P=0.007). p-QRS, paced QRS.

Table 3.

Univariate and Multivariate Analyses of Cardiac Death and Rates of Hospitalization for HF

	Univariate analysis			Multivariate analysis
	HR	95% CI	P value	HR	95% CI	P value
Age, 1-year increase	1.01	0.97–1.06	0.611
Men	1.06	0.42–2.79	0.899
Height, cm	1.02	0.94–1.04	0.633
Heart failure	2.47	0.57–7.59	0.200
Atrial fibrillation	2.86	1.13–7.52	0.028	2.28	0.89–6.03	0.084
RV septal pacing	0.59	0.22–1.49	0.262
Pre-QRS duration	1.01	0.99–1.03	0.079
p-QRS duration ≤149 ms	0.21	0.05–0.65	0.005	0.28	0.06–0.86	0.025
WN component	0.43	0.12–1.21	0.114
LVDd, 1 mm increase	1.09	1.01–1.16	0.021	1.07	0.99–1.14	0.101

CI, confidence interval; HR, hazard ratio. Other abbreviations as in Tables 1,2.

Various Parameters of Each QRS Duration

In patients with mid-range p-QRS duration (≤149 ms), the LV end-diastolic diameter and pre-QRS duration were significantly shorter than those in patients with longer p-QRS duration (>149 ms) (46±5 vs. 49±7%, P=0.008; 117±25 vs. 128±28%, P=0.003, respectively), although no significant difference was observed in the LVEF (60±6 vs. 59±7%, P=0.409; Table 4). RV septal pacing was more frequent in patients in the mid-range p-QRS duration group than in the long p-QRS duration group (78% vs. 50%, P<0.001). The WN waveform by retrograde penetration pacing into the conduction system via RV septal pacing was more frequent in patients in the mid-range QRS duration group than in the long QRS duration group (63% vs. 41%, P=0.003).

Table 4.

Baseline Characteristics of Patients With p-QRS Duration ≤149 ms and Those With p-QRS Duration >149 ms

	p-QRS duration ≤149 ms (n=89)	p-QRS duration >149 ms (n=98)	P value
Age, years	78±12	75±13	0.117
Men	41 (46%)	62 (63%)	0.020
Height, cm	157±9	160±10	0.046
Body weight, kg	55±12	59±12	0.016
ICM	18 (20%)	19 (19%)	>0.999
LVEF, %	60±6	59±7	0.409
LVDd	46±5	49±7	0.008
Pre-QRS	117±25	128±28	0.003
WN component	54 (61%)	23 (23%)	<0.001
RV septal pacing	69 (78%)	49 (50%)	<0.001
CDS	63 (71%)	47 (48%)	0.002

Data are expressed as mean±standard deviation or number (percentage). Abbreviations as in Tables 1,2.

Discussion

Main Findings

The main findings of this study were as follows: a p-QRS duration ≤149 ms was an excellent predictor of better clinical outcomes.

Predictors of Cardiac Events in Patients With Pacemakers

Pacemaker-induced cardiomyopathy and HF are observed in 10–20% of patients after pacemaker implantation.^5,7,8 Previous studies have reported that certain factors affect cardiac function after pacemaker implantation.^7–9 The p-QRS duration is a representative factor for predicting pacemaker-induced cardiomyopathy or HF, wherein the p-QRS duration that leads to pacemaker-induced cardiomyopathy or HF ranges from 140 to 167 ms.^8,13 In this study, a p-QRS duration >149 ms was seen to lead to cardiac events. In contrast, QRS duration, which prevents dyssynchrony, is shorter.¹⁰ Some patients with dyssynchrony due to RV pacing are expected to develop pacemaker-induced cardiomyopathy or HF. In patients with preserved EF who will undergo pacemaker implantation, a p-QRS duration ≤149 ms should be targeted to prevent cardiac events. An even shorter p-QRS duration may be required for pacemaker implantation in patients with a reduced EF to maintain the cardiac function and prevent HF hospitalization.

Association Between Cardiac Events and Pacing Site

A meta-analysis revealed that RV nonapical pacing maintains LVEF better than RV apical pacing.¹⁴ However, a recent study reported that the RV lead was positioned not at the RV septal wall but at the RV free wall or the anterior edge of the septal site in almost all patients.¹⁵ Therefore, the association between the pacing site and cardiac events remains controversial. A catheter delivery system can place the RV lead tip at the true RV septum, which leads to a shorter p-QRS duration compared with RV apex pacing.¹⁶ It should be noted that a shorter p-QRS duration is associated with LV synchrony.¹⁷ Based on these results, the effects of true RV septal pacing should be evaluated. In this study, patients without cardiac events had a shorter p-QRS duration than those with cardiac events. This result suggests that QRS narrowing using nonapical pacing through a catheter delivery system may reduce rates for hospitalization for HF. In addition, targeting the basal septal site of the RV may be preferable for reducing cardiac events.

Factors Affecting QRS Duration After Pacemaker Implantation

His bundle pacing and left bundle branch pacing reduced the p-QRS duration and hospitalization for HF, and it has been reported that this effect may replace cardiac resynchronization therapy.¹⁸ These pacing maneuvers can induce physiological ventricular activation using an intrinsic conduction system. Recently, it was reported that right bundle branch pacing preserved LV function and did not increase mortality rates as well as His bundle pacing.¹⁹ A part of RV septal pacing may allow more physiological pacing using an intrinsic conduction system such as the right bundle branch compared with RV apex pacing. A previous study reported retrograde penetration of the conduction system,¹⁰ wherein the QRS waveform, with W followed by N components, reflected the conduction of the ventricular myocardium and the conduction system, respectively. The pacing thorough the conduction system may maintain postoperative cardiac function. In this study, WN components were detected more frequently in patients with a p-QRS duration ≤149 ms than in those with a p-QRS duration >149 ms. Due to the shortening of the p-QRS duration, it may be necessary to select the area where the pacing stimulus captures the conduction system when choosing RV septal pacing using WN components as the indicator. In addition, 29% of patients with RV apical pacing had p-QRS duration ≤149 ms, and 20% of them had WN components. This result might suggest that even RV apex pacing can utilize the conduction system and shorten the p-QRS duration.

Study Limitations

First, this was a retrospective single-center study, and its results should be confirmed using prospective multicenter studies. Second, this study did not compare the clinical prognoses of true septal pacing using the catheter delivery system and non-true septal pacing. To resolve this issue, a randomized trial comparing the 2 methods should be performed. Third, we did not check echocardiographic data, especially in patients who were not hospitalized for HF. Therefore, the association between pacemaker-induced cardiomyopathy and hospitalization for HF remains unclear, and echocardiographic data should be collected in a prospective study. Fourth, the lead tip may have been unexpectedly implanted at the anterior edge in the patient for whom we decided the RV pacing leads were placed at the RV septum, as a computed tomography scan was not performed.

Conclusions

A p-QRS duration ≤149 ms was associated with a reduction in cardiac events. Therefore, it may serve as a target index of success in RV pacing.

Disclosures

K.K. and N.U. received honoraria for lectures from Medtronic Japan Co., Ltd.; K.I. received honoraria for lectures from Medtronic Japan Co., Ltd., JAPAN LIFELINE Co., Ltd., and Biotronik Japan, Inc.; S.N. is affiliated to a department endowed by Medtronic Japan Co. The authors declare no other possible conflicts of interest.

Funding

This research did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors.

IRB Information

This study was conducted in accordance with the principles outlined in the Declaration of Helsinki and was approved by the ethics committee of our institution (National Cerebral and Cardiovascular Center M26-150).

Supplementary Files

Please find supplementary file(s);

https://doi.org/10.1253/circj.CJ-24-0611

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