Diastolic mitral regurgitation after dual chamber pacemaker

Abstract

First-degree Atrioventricular (AV) block can lead to symptoms of heart failure, due to AV dyssynchrony. We report a case of 40-year-old male with symptomatic 2:1 AV block with intermittent first-degree AV block who was implanted with dual chamber pacemaker with conduction system pacing (CSP). With conventional programming of managed ventricular pacing (MVP) and long AV delays, patient developed dyspnea due to diastolic mitral regurgitation because of AV dyssynchrony. Hence, AV delay optimization was done, and the patient became asymptomatic with atrial sensing and 100 % ventricular pacing. This report emphasizes the importance of AV delay optimization in CSP for symptomatic benefit.

1. Introduction

Diastolic mitral regurgitation (MR) is observed during atrioventricular (AV) block of any degree when atrial contraction is not followed by adequately synchronized LV contraction. Effective ventricular contraction is mandatory for complete mitral valve closure. In the presence of first-degree AV block and severe LV dysfunction, dual-chamber pacing at a shorter AV interval may improve LV filling dynamics by optimization of mechanical atrial and ventricular synchrony, prolongation of the effective LV diastolic filling period, and elimination of diastolic MR. The combination of these factors may lower LV filling pressures and improve cardiac output, offering an additional therapeutic option for a subset of patients with severe LV dysfunction [1].

2. Case report

40-year-old male came with symptomatic 2:1 AV block and intermittent first-degree AV block. A dual chamber pacemaker (Biotronik) was implanted with a conduction system pacing lead. The paced QRS duration was 130ms and an LVAT was 75ms. The pacemaker was programmed with ventricular suppression (VS) algorithm and long AV delays (Fig. 1) [2]. He presented with symptoms of increasing breathlessness during follow-up at 6 months. All cardiac and non-cardiac causes of dyspnea were evaluated and ruled out. Interrogation revealed he was V-paced 39 % of the time. Echocardiography revealed normal left ventricular systolic function with no obvious structural abnormality but had AV dyssynchrony with fused E and A waves and significant diastolic MR (Fig. 2). AV delay optimization was performed under echo guidance. At a sensed AV delay of 150ms, E and A waves were optimally separated and there was a reduction of diastolic MR (Fig. 3). The device was reprogrammed (AV delay) and the VS algorithm was switched off to promote V pacing. The patient symptomatically improved and after 2 years of follow-up, patient continues to be asymptomatic with AS and V pacing 100 % (Fig. 4). This simple maneuver of optimizing AV delay in paced patients can improve hemodynamics, and reduce symptoms of heart failure.

Fig. 1.

12 lead ECG with Vp suppression algorithm on.

Fig. 2.

Fused E and A wave at AV delay of 200 ms with evidence of diastolic MR in pulse wave doppler at mitral inflow.

Fig. 3.

E and A wave separated with AV delay optimization to 150 ms and reduction of diastolic MR on pulse wave doppler at mitral inflow.

Fig. 4.

100 % ventricular pacing with optimized AV delay and Vp algorithm off.

3. Discussion

Several conditions lead to mitral regurgitation which typically occurs during ventricular systole. Diastolic MR can occur during AV dissociation and is a less common finding. Prolongation of PR interval leads to an early partial closure of the mitral valve in diastole in patients with AV block. Regurgitation during diastole occurs due to subsequent atrial contraction after a non-conducted P wave without ventricular systole [1]. Other conditions in which diastolic MR can occur include restrictive physiology or severe acute aortic regurgitation, atrial tachyarrhythmias such as atrial flutter with AV Block, and dilated cardiomyopathy [3]. Cardiac output correlates with inter-atrial conduction time. Inter-atrial and intra-atrial conduction time varies widely among pacemaker patients. Hence, the duration of the optimal AV interval has to be individualized [4].

Optimal AV interval should allow for the completion of end-diastolic filling flow prior to ventricular contraction. Excessively short or long AV intervals can have adverse hemodynamic consequences. Very short AV delay can truncate atrial filling, and unusually long AV delay may result in reduced cardiac output and diastolic MR. Atrial contribution to CO depends on the optimal AV interval, and it varies from 13 to 40 % [5]. The long-term loss of AV synchrony, i.e., inappropriately programmed AV interval is associated with electrical and mechanical atrial remodeling. This electrical and mechanical remodeling may result in atrial fibrillation and other atrial arrhythmias [6]. Conduction system pacing and CRT with optimized AV delay improves acute hemodynamic function in patients with heart failure and long PR interval.

Proper device evaluation and troubleshooting require a review of clinical and device history, a comprehensive and systematic clinical assessment of the patient and interrogation of the device and review of the ancillary data. Symptoms of fatigue, confusion, dypnea, orthopnoea, chest pain, palpitations, presyncope or syncope directs to investigate for either of pacemaker syndrome, loss of capture/pacing output, sensing abnormality, special algorithms, suboptimal rate modulated pacing or arrhythmias. Symptoms of hiccups needs to evaluate for LV/RA pacing close to phrenic nerve, RA lead dislodgement to SVC or lead perforation. Chest wall or pectoral muscle contractions need to look into unipolar pacing, loose set screw, lead insulation damage or lead perforation. Evaluating suspected pacemaker system malfunction based on presence or absence of ECG pacing stimuli guides us for further testing. Patients with no pacing stimuli, no intrinsic rhythm restoring with magnet suggest for oversensing issues while those not restoring tells more about conductor fracture, loose set screw, battery depletion or ODO/OVO modes. On the other hand patients with pacing stimuli, need to check for presence or absence of capture, thresholds and lead impedance; patients with high thresholds with rise or fall of impedance suggest for conductor fracture or insulation defect respectively while those high threshold patients with no change in lead impedance could be due to lead maturation, dislodgement, functional non capture or drug/metabolic causes. Patients with no change in thresholds and no appropriate timing of pacing stimuli are due to undersensing issues [7]. Adequate setting of AV delay allows to achieve electromechanical synchrony of atrial and ventricular systole which can have the positive outcomes on cardiac contractile function as well as on long term prognosis. Too short AVD abbreviates atrial systole and results in ventricular underfilling. Too long AVD causes diastolic MR. Both deleterious effect on cardiac output. Several echocardiographic parameters can be used to optimize AVD which include aortic VTI, iterative method, diastolic mitral flow pattern by ritter's method, diastolic filling time, doppler derived dP/dt, VTI of mitral inflow, tissue doppler imaging and myocardial performance index [8].

In our case (Biotronik dual chamber pacemaker with conduction system pacing), the algorithm used to reduce unnecessary ventricular pacing is the VP suppression algorithm. In ADI(R) mode, intrinsic conduction is monitored within a 450ms interval after each atrial event. A cycle without intrinsic ventricular conduction triggers a further 8-cycle evaluation period. If any of the following criteria are met, the device reverts to DDD(R): (i) 2 consecutive cycles without intrinsic ventricular conduction (ii) a programmable number (1–8) out of 8 cycles without intrinsic conduction (iii) no VS event for 2 or more seconds. When VP suppression is on, the pacemaker will not switch to DDD unless the PR interval exceeds 450 ms [2]. The results of BIOPACE, BLOCK-HF, ANSWER, CanSaveR, and MADIT-CRT suggest the possibility that, in patients with normal ventricular function and intermittent AVB, allowing native conduction and minimizing VP is the preferred option. Among patients with LV systolic dysfunction and significantly prolonged PR interval, a biventricular device shall be preferred to a conventional DDD pacemaker. These results are in line with previous findings in a large community-based cohort study, where a PR interval >200 ms was associated with a 2-fold increased risk of AF onset when compared with a shorter PR interval [9]. The issue of PR prolongation is probably even more important in patients with AVB. In our patient, the VP suppression algorithm was switched off and AV delay was optimized using echocardiography. This resulted in optimal separation of E and A waves, reduction of diastolic MR and symptoms of HF resolved.

Learning points

Among patients with a pacemaker with no other identified cause of dyspnea, optimizing AV delay results in improved ventricular filling and reduced left atrial pressure. While VP suppression algorithm is useful it is not for all patients.

Statement of consent

The authors certify that they have obtained patient informed consent for publication.

Funding

None.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.