DDD mode-switching and loss of atrioventricular synchrony evokes heart failure: A rare but possible trigger of pacing-induced cardiomyopathy

Abstract

Pacing-induced cardiomyopathy (PICM), defined as left ventricular dysfunction, occurs in the setting of chronic, high burden right ventricular pacing. We describe an unusual case of PICM. A 64-year-old man underwent a medical check-up and was diagnosed with complete atrioventricular block (AVB) with regular and slow ventricular contractions at 38 beats/min (bpm). The patient underwent a pacemaker implantation with a dual-chamber pacing (DDD) pacemaker. This patient had no symptoms or signs of PICM during complete AVB or the period after undergoing dual-chamber pacing. However, PICM developed within a short time after the onset of atrial flutter (AFL). During AFL, the automatic mode switch of the DDD pacemaker to the DDIR mode worked normally, and the ventricles were paced with a stable and regular rate (60 bpm). Despite the administration of ß-blockers and diuretics, his symptoms and status did not improve. After the elimination of the AFL and restoration of AV synchrony with a DDD mode by catheter ablation, the deteriorated condition rapidly improved. In this patient, the coexistence of the loss of AV synchrony and high burden RV pacing during AFL might have caused this unusual PICM.

Learning objective: Even when patients have no symptoms or signs of pacing-induced cardiomyopathy (PICM) during complete atrioventricular block or the period after undergoing dual-chamber pacing, automatic mode-switching to the DDI mode during atrial tachyarrhythmias could rapidly cause PICM. PICM could occur with a much more rapid time course than the historical model of PICM where cardiomyopathy may take several years to develop. Much attention should be paid during the follow-up to patients receiving DDD pacemakers to avoid any unusual PICM as in this case.

Introduction

High burden right ventricular (RV) pacing can lead to progressive potentially deleterious effects on left ventricular (LV) function, which are known as pacing-induced cardiomyopathy (PICM) [1]. PICM is increasingly recognized as a common and important cause of heart failure (HF) in patients with atrioventricular block (AVB) after pacemaker implantation [2], [3], [4].

We describe here a patient who received a dual-chamber pacing (DDD) pacemaker for complete AVB. In this patient, no PICM occurred during periods of complete AVB or dual-chamber atrioventricular (AV) pacing. However, during stable and regular RV pacing with a DDIR mode [60 beats/min (bpm)] during atrial flutter (AFL), the patient developed PICM within a short time. After the elimination of the AFL and restoration of AV synchrony with a DDD mode by catheter ablation, that deteriorated condition rapidly improved. Thus, this case is an unusual case of PICM.

Case report

A 64-year-old man suffering from dyspnea with mild effort was referred to our hospital for further evaluation of HF and arrhythmias. Thirteen months previously, he underwent a medical checkup and was diagnosed with complete AVB with regular and slow ventricular contractions at 38 beats/min (bpm; Fig. 1A). At that time, he had no symptoms, and his condition was New York Heart Association (NYHA) functional class I. Chest radiography revealed no cardiac enlargement [cardiothoracic ratio (CTR), 46%]. Echocardiography revealed no LV dilatation with a normal function [LV ejection fraction (LVEF)=54%, Fig. 1B]. There was no increase in the left atrial (LA) diameter or volume. The serum B-type natriuretic peptide (BNP) level was mildly elevated at 99.8 pg/ml. Coronary angiography and right ventricular endomyocardial biopsy disclosed no findings suspicious of secondary myocardial disease. Magnetic resonance imaging revealed no late gadolinium enhancement in the myocardium and the gallium-67 scintigraphy was negative. He underwent a pacemaker implantation with a DDD pacemaker (Azure XT DR MRI W2DR01; Mode switch, Medtronic Inc., Minneapolis, MN, USA). The atrial and ventricular pacing leads were implanted in the right atrial appendage and mid septum of the right ventricle, respectively (Fig. 1C). The pacemaker settings were a DDD mode (60–130 bpm) with mode switching. The programmed mode switch was set to an atrial rate of >171 bpm (DDIR mode). The patient had >95% ventricular pacing as determined by the device diagnostic data (Fig. 1D). One month after the pacemaker implantation, electrocardiography revealed sinus rhythm with DDD pacing (Fig. 2A).

Fig. 1.

(A) Electrocardiographic tracing during 24-h Holter monitoring. Complete atrioventricular block with regular and slow ventricular contractions (38 beats per minutes), independent of the P waves, was found. (B) Transthoracic echocardiogram before the pacemaker implantation. The echocardiography disclosed a normal left ventricular ejection fraction. (C) Chest X-ray film shortly after the DDD pacemaker implantation. The cardiothoracic ratio is 48%, and the tip of the ventricular pacing lead is positioned at the lower septum of the right ventricle (arrow). (D) Cardiac Compass^Ⓡ Trends (Medtronic). With the onset of atrial flutter (AFL), no atrial pacing occurs. During AFL, the average (Avg) rate of the ventricular pacing decreases, and it is stable at 60 beats per minute (bpm) at night, suggesting the automatic mode switch to the DDIR mode had worked normally. AFL started 3 months before the catheter ablation (10 months after the pacemaker implantation).

AF, atrial fibrillation; AT, atrial tachycardia; Dd(s), end-diastolic (end-systolic) diameter; EF, ejection fraction; LAD, left atrial diameter; LV, left ventricular.

Fig. 2.

The 12-lead electrocardiograms. (A) One month after the pacemaker implantation (DDD mode, 60–130 beats/min). (B) During atrial flutter before the catheter ablation. (C) After the ablation.

During the following 10 months after the pacemaker implantation, he was well with no symptoms and an NYHA functional class I. The echocardiographic parameters and CTR 3 months after the pacemaker implantation were all comparable with those before the pacemaker implantation during complete AVB (Fig. 3A). The serum BNP level was 54.4 pg/ml.

Fig. 3.

Serial changes in the echocardiographic images and parameters. The left atrial (LA) size and left ventricular (LV) size and function after the pacemaker implantation are comparable to those before receiving the pacemaker during complete atrioventricular block. After the onset of atrial flutter (AFL), the LA and LV size increased, and the LV function decreased. Those changes dramatically improved 3 months after the AFL elimination by catheter ablation. (A): Three months after the pacemaker implantation. (B): Before the AFL ablation. (C): Three months after the AFL ablation.

Dd(s), diastolic (systolic) diameter; EF, ejection fraction; LAD, left atrial diameter; PM, pacemaker.

Three months previously, he experienced dyspnea with mild effort and saw a doctor at the hospital where he had undergone the pacemaker implantation. The electrocardiogram (ECG) showed AFL and regular ventricular pacing, which was the result of automatic mode-switching during AFL. Despite the administration of ß-blockers (bisoprolol, 2.5 mg/day) and diuretics (spironolactone, 25 mg/day), his symptoms did not improve, and therefore, he was referred to our hospital.

Upon admission at our hospital, his condition had deteriorated to a NYHA functional class III. Chest radiography showed further cardiac enlargement (CTR, 51%), and the serum BNP level had increased to 199.3 pg/ml. Echocardiography disclosed increased LV dimension, diffusely hypokinetic LV wall motion (LVEF,= 33%), and increased LA dimension and volume (Fig. 3B). No apparent interventricular dyssynchrony was found. The ECG showed AFL and regular ventricular pacing at 60 bpm. The AFL waves were predominantly negative in leads II, III, aVF, and V6, and positive in lead V1, with a regular rate of 300 bpm (Fig. 2B). The interrogation of the pacemaker disclosed approximately 100% daily ventricular pacing after the AFL onset (Fig. 1D). The ventricular pacing rate was stable at 60 bpm at night (Fig. 1D). Those findings suggested that the automatic mode switch to the DDIR mode had worked normally.

An electrophysiologic study disclosed that the tachycardia was a cavo-tricuspid isthmus dependent, counterclockwise AFL. With radiofrequency catheter ablation at the isthmus, the AFL terminated, and sinus rhythm was restored. Finally, bidirectional conduction block at the isthmus was created. The pacemaker was set to the DDD mode, and AV synchrony with an atrial sense ventricular pace was restored (Fig. 2C).

After restoration of the AV synchrony, his symptoms and cardiac status dramatically improved. Three months post-ablation, the CTR and serum BNP level had decreased to 46% and 45.1 pg/ml, respectively. The LV internal dimension and LA dimension and volume also had decreased, but the LVEF had increased to 61% (Fig. 3C). The patient has done well with no deterioration of the HF or occurrence of any tachyarrhythmias during 10 months of follow-up.

Discussion

Our case showed the following findings: 1) the patient developed complete AVB with a regular but slow ventricular rhythm, but had no symptoms or any apparent signs of HF; 2) after receiving a DDD pacemaker, he was well with no HF signs for 10 months; 3) his condition deteriorated rapidly after the onset of AFL with a regular ventricular pacing function of the automatic mode switch (DDI mode, 60 bpm), and LV dilatation with a hypokinetic LV and increased LA size developed and progressed; and 4) after the elimination of the AFL and restoration of AV synchrony with the DDD mode, his symptoms and cardiac status dramatically improved. Thus, in this case, no apparent overt HF symptoms were found during the loss of AV synchrony during complete AVB or while receiving DDD pacing for the AVB. That became rapidly apparent only after the ventricles became fully contracted by pacing with a regular and adequate rate during AFL. Unfortunately, the data including the systolic and diastolic function independent of the heart rate (e.g. strain analysis, Tei index) could not be evaluated with echocardiographic examinations in this patient. However, from the findings described above, we think that this is a very unusual case of PICM.

In patients with AFL, rapid and uncontrollable ventricular contractions sometimes trigger cardiac dysfunction and HF, which is known as a tachycardia-induced cardiomyopathy [5]. However, in our case, the ventricular pacing rate was regular and stable at 60 bpm when his HF developed and progressed. Therefore, the possibility of tachycardia-induced cardiomyopathy was extremely low. Recently, atrial fibrillation-induced cardiomyopathy (AF-CM) has been defined as LV systolic dysfunction in patients with paroxysmal or persistent atrial fibrillation despite appropriate rate control. AF-CM is considered to be triggered in part due to a heart rate irregularity and loss of atrial contraction/emptying [6]. Although the ventricular pacing rate was stable at 60 bpm and no heart rate irregularity was observed in our case, we could not completely deny the prospect of AF-CM. PICM is most commonly defined as a drop in the LVEF in the setting of chronic, high burden RV pacing. It has been reported that ~20% of patients develop PICM after 3–4 years of RV pacing [1]. Previous studies reported that the incidence of PICM did not differ between dual-chamber and single-chamber pacing [2,7]. In our case, the patient did not develop any overt HF during the complete AVB (state of a loss of AV synchrony) or dual-chamber AV pacing with high burden RV pacing, suggesting that the loss of AV synchrony or high burden RV pacing was not the sole reason for the development of HF. The HF developed only during stable and regular RV pacing during AFL when the automatic mode switch normally worked. We believe that, although rare, the coexistence of a loss of AV synchrony and high burden RV pacing caused overt HF in this patient.

Recent studies have disclosed a much more rapid time course of the development of HF following a pacemaker implantation than the historical model of PICM where cardiomyopathy may take several years to develop [3,8]. The risk of PICM is high in the first 6 months after pacemaker implantations for heart block [3,8]. Electrical and mechanical remodeling of the atria are caused by the loss of AV synchrony during VVI pacing for 3 months, and those reverse after reestablishing AV synchrony with DDD pacing for the following 3 months [9,10]. As stated above, PICM may help to explain the cardiac function decline in our patient. The PICM progressed during stable and regular RV pacing with AV dyssynchrony within a short time. Furthermore, shortly after the restoration of AV synchrony and sinus rhythm with DDD pacing by the AFL ablation, the PICM dramatically improved with a normal cardiac function and chamber size within 3 months. Our case highlighted that, in AVB patients receiving DDD pacemakers, even when the patients have no signs of PICM during complete AVB or the period after undergoing dual-chamber pacing, and changing from DDD pacing to single-chamber RV pacing with automatic mode-switching during atrial tachyarrhythmias could rapidly evoke PICM, and that restoration of AV synchrony by catheter ablation and DDD pacing could improve the PICM within a short time.

Declaration of Competing Interest

Hiroshi Tada received honoraria (lecture fees) from Daiichi-Sankyo Co., Ltd., Biotronik Japan, Inc., Bristol-Myers Squibb, and Boehringer Ingelheim. Shinsuke Miyazaki received honoraria (lecture fees) from Daiichi-Sankyo Co., Ltd., Medtronic Japan, Co., Ltd., Bristol-Myers Squibb, and Boehringer Ingelheim.