Cardiac resynchronization therapy-defibrillator implantation in isolated left ventricular apical hypoplasia

Introduction

Isolated left ventricular apical hypoplasia (ILVAH) is an extremely rare and unclassified cardiomyopathy. The true apex is occupied by the right ventricle, which wraps around the distal left ventricle. It is known to be associated with heart failure and risk of malignant arrhythmias. Treatment of ILVAH is individualized, focusing on heart failure optimization and ventricular arrhythmia management.

Case presentation

A 54-year-old gentleman presented with reduced exercise tolerance for 1 year. He was diagnosed with dilated cardiomyopathy in Year 2024. He had no family history of sudden cardiac death. Transthoracic echocardiogram showed global hypokinesia, left ventricular ejection fraction (LVEF) of 14% with aneurysmal septum, and akinetic anterior wall. The apical four-chamber view showed elongation of the right ventricle apex wrapping around the deficient left ventricle apex (Figure 1, Panel A). Coronary angiogram revealed minor coronary artery disease.¹ ILVAH was diagnosed based on transthoracic echocardiogram and cardiac magnetic resonance imaging (MRI) findings.² He had features of truncated spherical left ventricle, elongated right ventricle wrapping around left ventricle apex, interventricular septum bowing towards right ventricle in diastole, and infiltration of adipose tissue in left ventricle apex (Figure 1, Panel D, E).³ Cardiac MRI showed subendocardial fibrosis at basal anterior septum of myocardium segment as evidenced by late gadolinium enhancement (Figure 1, Panel F, G). He underwent implantation of a cardiac resynchronization therapy defibrillator (Quadra Assura MP™ cardiac resynchronization therapy-defibrillator [CRT-D]) for non-ischaemic dilated cardiomyopathy. This was indicated by persistent NYHA class II symptoms despite optimal tolerated guideline-directed medical therapy (GDMT) consisting of oral Entresto 50 mg BD, dapagliflozin 10 mg OD, bisoprolol 5 mg OD, and spironolactone 25 mg OD. During the admission, the patient was counselled for genetic analysis as part of a further work-up for ILVAH and its potential correlation with genetic predisposition. The patient was followed up at 1, 3, 6, and 12-month intervals in a device and heart failure clinic. During this period, medications were optimized to oral Entresto 100 mg BD, dapagliflozin 10 mg OD, bisoprolol 10 mg OD, and spironolactone 25 mg OD. Pre CRT-D implant electrocardiogram showed intraventricular conduction delay with QRS duration 146 ms (Figure 1, Panel B). The left ventricle coronary sinus lead (Quartet^TM 1456Q) was positioned into the lateral branch of the coronary sinus. The right ventricle DF-4 defibrillator lead (Durata^TM 7122Q) was positioned to the right ventricular septum. Device optimization post CRT-D implant by pre-exciting the left ventricle by 15 ms ahead of the right ventricle yields a narrow QRS duration of 116 ms (Figure 1, Panel C). One-year post-implantation patient had events of non-sustained ventricular tachycardia with a cycle length of 347 ms terminating spontaneously (Figure 1, Panel H,I). A repeat echocardiogram in 1 year showed improved LVEF to 51% with NYHA class I. This patient was a cardiac resynchronization therapy responder as evidenced by the results of transthoracic echocardiographic evaluation with improvement in LVEF from 14% to 51%, together with a reduction in left ventricular end systolic volume from 162 to 94 mL.

Figure 1.

(Panel A) Transthoracic echocardiogram apical 4-chamber view showing elongation of right ventricle apex wrapping around deficient left ventricle apex. (Panel B) Pre-CRT-D implant 12-lead electrocardiogram showing intraventricular conduction delay with QRS duration of 146 ms. (Panel C) Post-CRT-D implant 12-lead electrocardiogram with narrow QRS duration of 116 ms. (Panel D) Cardiac MRI features of elongation of right ventricle apex wrapping around deficient left ventricle apex and infiltration of adipose tissue in left ventricle apex. (Panel E) Cardiac MRI features of interventricular septum bowing towards right ventricle in diastole and truncated spherical left ventricle. (Panel F, G) Cardiac MRI late gadolinium enhancement (LGE) features of subendocardial fibrosis in basal anterior septum of left ventricle myocardium segment. (yellow marker) (Panel H, I) Cardiac implantable electronic device (CIED) electrogram showing episode of non-sustained ventricular tachycardia with a cycle length of 347 ms.

Discussion

ILVAH is a very rare congenital heart anomaly with a high probability of linkage to Lamin A/C or NEXN gene mutations, which can be easily missed in early stages, and hence targeted imaging tools will help establish the diagnosis. This patient showed a good clinical response within 1-year post CRT-D with optimally tolerated GDMT.⁴ CRT-D SyncAV^TM technology may also help restore atrioventricular (AV) synchrony in patients with preserved intrinsic conduction. It is designed to optimize CRT by enabling fusion pacing. The SyncAV^TM algorithm periodically extends the AV delay (every 256 cardiac cycles for 3 consecutive beats) to measure the patient's own intrinsic PR interval. It then sets the pacing AV delay at a specific, shorter interval before the native ventricular activation occurs. A new AV delay is set by subtracting a programmable SyncAV offset (default value of −50 ms) from the measured intrinsic sensed AV interval.^5,6 The 2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy state that CRT should be considered for symptomatic patients with heart failure in sinus rhythm who present with a QRS duration of 130–149 ms, an LVEF ≤ 35%, and left bundle branch block (LBBB) QRS morphology despite optimal medical therapy. Conversely, CRT is indicated for patients with a QRS duration of 150 ms or more if they exhibit the same LBBB morphology, LVEF, and clinical symptoms. Furthermore, the guidelines note that CRT may be considered for symptomatic patients presenting with a non-LBBB QRS morphology, a QRS duration of 130–149 ms, and an LVEF ≤35%. Supporting this, a 2023 multicentre patient-level meta-analysis of randomized controlled trials by Friedman et al., titled ‘Cardiac Resynchronization Therapy Improves Outcomes in Patients With Intraventricular Conduction Delay But Not Right Bundle Branch Block,’ analysed data from pivotal CRT trials (including MIRACLE, MIRACLE-ICD, MIRACLE-ICD II, REVERSE, RAFT, BLOCK-HF, COMPANION, and MADIT-CRT). The analysis demonstrated that patients with intraventricular conduction delay, especially those with QRS duration 150 ms or more, benefit from CRT, showing a significant reduction in heart failure hospitalizations or death.^7,8 The LOT-CRT technique described by Jastrzebski et al. and the Reverse LOT-CRT technique described by Clementy et al. are viable options for patients with distal conduction system disease not corrected by conventional pacing. However, management should be tailored to the individual patient to ensure a favourable outcome.⁹ The use of CRT-D Futility score for decision-making prior to CRT-D is advisable for a better clinical outcome. This patient had a CRT-D Futility score of 1, which led to implantation of CRT-D rather than CRT-P.¹⁰ The presence of subendocardial fibrosis in the basal anterior septum of myocardium segment on cardiac MRI can be an arrhythmogenic substrate for malignant arrhythmias. The nature of arrhythmogenic substrate progression for ILVAH is not well known with limited data, and hence a meticulous approach is needed in the management of these rare groups of patients. Hence, this case underscores the need for thorough risk assessment before CRT-D implantation in non-ischaemic cardiomyopathy patients. Pre-implantation evaluation is critical to effectively mitigate the risk of sudden cardiac death from malignant ventricular arrhythmias.

Author contributions

Kunaraj Perumalu (Writing—original draft, Writing—review & editing [lead]), Saravanan Krishinan (Supervision [lead]), Barakath Badusha Abdul Kareem (Supervision [supporting]), and Mohamed Jahangir Abdul Wahab (Supervision [supporting])

Supplementary material

Supplementary Material is available at European Heart Journal – Case Reports Online.

Consent: The authors confirm that written consent for submission and publication of this case report including images and associated text has been obtained from the patient in line with COPE guidelines.

Funding

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

Data availability

The data underlying this article will be shared on reasonable request to the corresponding author.