Why Cardiac Resynchronization Therapy (CRT) For complete heart block? A case discussion

P. Selva Maheshwari1, Dr. S. Deep Chandh Raja2,*

1Physician Assistant, Unit of Cardiac Electrophysiology, Kauvery Heart Rhythm Services, Chennai

2Cardiologist and Clinical Lead of Cardiac Electrophysiology, Kauvery Heart Rhythm Services, Chennai

*Correspondence: drdeepchandh@kauveryhospital.com


Cardiac Resynchronization Therapy (CRT) is a procedure to implant a device using simultaneous pacing of the right ventricle and left ventricle (biventricular pacing). CRT is indicated in patients with low ejection fraction (typically LVEF ≤ 35%). Biventricular pacing is achieved by a lead placed in a tributary of the coronary sinus for LV pacing, in addition to leads in the RV and RA. These leads are attached to a pulse generator, which is usually placed in the subcutaneous tissue of the chest. Cardiac resynchronisation therapy could be either with a CRT pacemaker (CRT – p) device or a combined CRT – implantable cardioverter defibrillator (CRT – d) device. The beneficiaries of this therapy are usually patients with symptoms of heart failure and electro-mechanical dyssynchrony as evidenced by left bundle branch block (LBBB) on the ECG with QRS duration > 140 msec [1]. However, there are cardiac conditions where CRT is preferred in the absence of a left bundle branch block. In the case below, we describe CRT as a mode of therapy for a patient presenting with heart failure, and complete heart block.

Case Presentation

A 60-year-old male came with complaints of dyspnoea for the last 1 month with paroxysmal nocturnal dyspnea (NYHA class III). The patient had diabetes mellitus and hypertension. The patient was also known to have Pott’s spine with a history of surgical fusion of thoracic lumbar vertebrae. Based on her history and previous records, he was also known to have dilated cardiomyopathy with severe LV dysfunction and has been on optimal heart failure medications for the last 5 years. Chest x-ray showed severe cardiomegaly with grade III pulmonary venous hypertension. (Fig. 1A) Clinically, the patient had an elevated JVP (Video 1). Echo revealed severe LV dysfunction (LVEF 20–25%) with moderate mitral regurgitation and dilated LV. (Fig. 1B) The patient had a narrow QRS in the previous ECGs. However, the current ECG revealed a complete heart block with a wide QRS escape rhythm (RBBB with left anterior hemiblock). (Fig. 2A).


Fig. 1. Panel A is the Chest X-ray PA view of the patient which shows cardiomegaly with increased pulmonary vascular markings and Kerley C lines suggestive of severe pulmonary venous hypertension; Panel B is the Echocardiography picture which shows the dilated left ventricle with poor ejection fraction (diastolic frame).


Fig. 2. Panel A shows the 12-lead ECG at presentation showing complete heart block with wide QRS escape rhythm; Panel B shows the 12-lead ECG after the device implant with biventricular pacing- note the QRS duration which is 120 ms.

This patient was taken up for a coronary angiogram, which revealed recanalised left anterior descending vessel suggesting that the cardiomyopathy was probably of ischaemic aetiology. An electrophysiology study revealed Infra-Hisian complete heart block with ventricular escape rhythm. Under general anaesthesia, the patient had a successful CRT-d implant (MedtronicR with Attain StabilityR CS lead). (Fig. 3A and B). Immediately after the procedure, the patient’s haemodynamics, renal parameters and general condition improved. The patient was extubated on day 1 and was observed in the wards for 7 days for titration of heart failure medications. The patient came back to the Heart Failure Clinic after 1 month with minimal symptoms of heart failure (NYHA class I) and normal blood parameters of electrolytes and renal functions. The left ventricular ejection fraction had improved to 35%. Biventricular pacing resulted in a QRS duration of 120 ms on the 12-lead ECG. (Fig. 2B).


Fig. 3: Panel A shows the fluoroscopic image of the CRT-d in AP view with the implanted right ventricular (RV) and left ventricular (LV) pacing leads; Panel B shows the fluoroscopic image of the CRT-d in RAO view with the implanted right ventricular (RV) and left ventricular (LV) pacing leads.


We have described a patient of dilated ischaemic cardiomyopathy with severe LV dysfunction presenting with acute decompensated heart failure due to new onset complete heart block. This patient received CRT-d implant considering the need for 100% RV pacing and the risk of sudden cardiac death in the future.

While the above-described patient was doing well on optimal medical therapy despite severe LV dysfunction, the onset of complete heart block seems to have worsened his heart failure. Hence the patient presented with acute heart failure. A routine pacemaker with a right ventricular pacing lead would be could have been the device of choice. But it is important to consider that such a patient with severe LV dysfunction is likely to worsen because of RV-pacing induced electro-mechanical dyssynchrony. BLOCK-HF study analyzed biventricular versus right ventricular pacing in heart failure in patients with LVEF < 50% age and AV block [2]. The study showed improvement reduction in the primary outcome of death and heart failure re-hospitalization. As a result, the American College of Cardiology (2022 heart failure) guidelines, have given a class IIA recommendation to CRT as a mode of therapy for heart failure patients with LVEF < 50% presenting with a high degree of complete heart block [1].

Furthermore, it is being contemplated that patients requiring >40% RV pacing with mild left ventricular dysfunction are likely to benefit from biventricular pacing [3]. Also, patients with pacing-induced cardiomyopathy and post-AV node ablation for atrial fibrillation will benefit from biventricular pacing [4,5].


We have presented a patient with a case of ischaemic cardiomyopathy with worsening heart failure due to a complete heart block who benefited from CRT-d. This case is to highlight the importance of identifying the right heart failure device therapy appropriate for a given patient. We have also discussed the group of patients who are likely to benefit from biventricular pacing.


[1] Heidenreich PA, et al. 2022 AHA/ACC/HFSA guideline for the management of heart failure: a report of the American college of cardiology/American heart association joint committee on clinical practice guidelines. Circulation 2022;145:e895-e1032. [2] Curtis AB, et al. Biventricular pacing for atrioventricular block and systolic dysfunction. N Engl J Med 2013;368:1585-93. [3] Kusumoto FM, et al. 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay: a report of the American college of cardiology/American heart association task force on clinical practice guidelines and the heart rhythm society. Circulation 2019;140:e382-e482. [4] Adelstein E, et al. Predicting hyper response among pacemaker-dependent nonischemic cardiomyopathy patients upgraded to cardiac resynchronization. J Cardiovasc Electrophysiol. 2011;22:905-11. [5] Doshi RN, et al. Left ventricular-based cardiac stimulation post AV nodal ablation evaluation (the PAVE study). J Cardiovasc Electrophysiol. 2005;16:1160-5.

Video 1 shows the elevated Jugular Venous Pressure as noted by the JVP waveforms above the clavicle in sitting position (Video attached)


Dr. S. Deep Chandh Raja

Cardiologist and Clinical Lead of Cardiac Electrophysiology