Neither Unclassified nor Acquired Dilated Cardiomyopathy: LEFT Bundle Branch Block induced Cardiomyopathy in search of its RIGHT place! (QF_SA_116)

A 68 years old male, known case of Type 2 Diabetes Mellitus , Systemic Hypertension, Dyslipidemia, and a Non-obstructive Coronary Artery Disease on CT Coronary Angiography  done twice in 2019 and 2023.

An Echocardiography examination showed Severe LV Dysfunction with an Ejection Fraction of 25%. He was found to have Left bundle branch block on the ECG with a QRS duration of 150ms.

He is relatively asymptomatic. He has no dyspnea on exertion / angina/ palpitations/ presyncope/ syncope.

His vitals were Stable with unremarkable General and Physical examination findings. He is maintaining well on Optimal Medical Therapy. 

Diagnostic Techniques and Their Most Important Findings:

Diagnostic Technique:

ECG-gated cardiovascular MRI was performed on 1.5 T magnet. A total of 17 cc of intravenous Gadolinium DTPA given . Sequences include

T1/T2 IR FSE, Cine SSFP in [short and long axis], Q flow imaging across proximal ascending aorta, main pulmonary artery and transmitral plane.

Rest Perfusion and Myocardial Viability (Delayed Enhancement), [0.2mmol/kg] Gadolinium was given intravenously. First pass myocardial perfusion was performed at rest only, followed by 10 min delayed enhancement in short and long axis.

Images were post-processed and analyzed on a dedicated cardiac MR workstation.

Findings:

The patient is found to have Dilated LV cavity with preserved wall thickness and mildly hypertrabeculated basal and mid lateral wall and apical cavity. Both atria and right ventricle appear normal in size with Severe LV systolic dysfunction with LVEF-25%. There is no LV clot.

Regional wall motion abnormality with intersegmental dys-syncronous contraction is noted. There is hypo-contractile IVS in pre-ejection phase followed by good contractile lateral wall after time lag with paradoxical movement of interventricular septum towards RV, features of which are consistent with LBBB.

There is No evidence of delayed hyper-enhancement in LV and RV myocardium. There is No evidence of fibrosis/infiltration or acute myocardial injury in LV myocardium.

In view of non-obstructive coronary disease, above findings possibly suggestive of LBBB induced cardiomyopathy with no myocardial fibrosis or infiltration seen

 

Learning Points from this Case:

1. LBBB induced Cardiomyopathy, despite being a separate entity, remains unlabelled: it is neither regarded as an unclassified cardiomyopathy nor does it have an acquired or non-genetic forms of cardiomyopathy. 

2. There is little evidence regarding cardiac remodelling and LV improvement after Optimal medical therapy in such patients

3. Questions still remain unanswered regarding early initiation of CRT therapy in patients with LBBB induced Cardiomyopathy and its prognosis, long term outcomes and durable benefits of CRT therapy  

4. CMR needs to find convincing ways to find aetiology in cases of Dilated Cardiomyopathy, one of which is LBBB-induced cardiomyopathy which has a complex potential interaction between genetic background and an electric persistent milieu.