HNOCM with MR

HNOCM with MR

HNOCM with MR
HNOCM with MR

Colour Doppler echocardiogram from parasternal long axis (PLAX) view in hypertrophic nonobstructive cardiomyopathy (HNOCM) showing a grossly thickened interventricular septum (IVS). Posterior wall of the left ventricle does not show much hypertrophy. This type of hypertrophy is called asymmetric septal hypertrophy and is characteristic of hypertrophic cardiomyopathy. A bluish mosaic coloured jet of mitral regurgitation (MR) is seen in the left atrium (LA) during systole, when the mitral valve is closed. Please note that there is no narrowing of the left ventricular outflow  tract (LVOT) in systole. The flow in the LVOT is laminar, without any mosaic pattern. There is no systolic anterior movement (SAM) of the anterior mitral leaflet which is the important cause of LVOT obstruction in hypertrophic cardiomyopathy.

The frame on the right side is a diastolic frame with the mitral valve open. Left atrium (LA) is dilated,  twice the aortic (Ao) diameter or more. Right ventricle (RV) and left ventricle (LV) are not enlarged. Left ventricular cavity may enlarge in the late dilated phase of hypertrophic cardiomyopathy.

TDI (tissue Doppler imaging) in hypertrophic nonobstructive cardiomyopathy showing pattern suggestive of left ventricular diastolic dysfunction. A’ (during atrial systole) is of higher amplitude than E’ (early diastolic). Normally the E’ wave is of higher amplitude than the A’ wave. Upper panel shows the colour kinesis two dimensional image from the apical four chamber view which shows that TDI sampling is from the medial (septal) mitral annulus.

Tissue Doppler Imaging in HNOCM showing LV diastolic dysfunction
Tissue Doppler Imaging in HNOCM showing LV diastolic dysfunction

An interesting case of hypertrophic cardiomyopathy initially thought to be non obstructive, developing a graident more than 100 mm Hg with fall in arterial pressure in the post exercise period has been reported [1]. Left ventricular outflow gradient did not occur at peak workload. But an intraventricular gradient of 110 mm Hg was documented in orthostatic position after exercise. There was a fall in systolic blood pressure from 130 mm Hg to 110 mm Hg and the patient was then put in supine position. It was associated with systolic anterior movement of anterior mitral leaflet. This was after 9 minutes of exercise on treadmill with standard Bruce protocol. She gave history of syncope after playing basket ball.

Higher arrhythmic risk in non obstructive HCM than in obstructive HCM has been reported by Lu DY et al [2]. In their study of 705 HCM patients, of which 230 had obstruction, sustained ventricular tachycardia/ventricular fibrillation was more likely in non obstructive HCM. They were more likely to have an implantable cardioverter defibrillator. Atrial fibrillation was most frequent in the obstructive group.

References

  1. Cotrim C, Almeida AR, Lopes L, Fazendas P, João I, Pereira H. What is really a nonobstructive hypertrophic cardiomyopathy? The importance of orthostatic factor in exercise echocardiography. ISRN Cardiol. 2011;2011:346797.
  2. Lu DY, Pozios I, Haileselassie B, Ventoulis I, Liu H, Sorensen LL, Canepa M, Phillip S, Abraham MR, Abraham TP. Clinical Outcomes in Patients With Nonobstructive, Labile, and Obstructive Hypertrophic Cardiomyopathy. J Am Heart Assoc. 2018 Feb 25;7(5):e006657.