Left ventricular function in patients with hypertrophic cardiomyopathy and its relation to myocardial fibrosis and exercise tolerance

Abstract

We sought to determine the relation between myocardial extracellular volume (ECV), left ventricular (LV) diastolic function, and exercise tolerance in patients with hypertrophic cardiomyopathy (HCM). Forty five HCM patients with an ejection fraction >50% and no previous septal reduction therapy underwent imaging by CMR and transthoracic echocardiography. CMR was used to quantify LV volumes, mass, EF, LA volumes, scar burden, pre and post contrast T1 relaxation times and ECV. Echocardiography was used to measure outflow tract gradients, mitral inflow and annular velocities, circumferential strain, systolic, early and late diastolic strain rates. Exercise duration and peak oxygen consumption were noted. HCM patients had increased native T1 relaxation time and ECV vs. controls [ECV controls: 24.7 (23.2-26.4) vs. HCM: 26.8 (24.6-31.3)%, P = 0.014]. Both parameters were significantly associated with LV diastolic dysfunction, circumferential strain, diastolic strain rate and peak oxygen consumption (r = -0.73, P < 0.001). Compared to controls, HCM patients have significantly longer native T1 relaxation time and higher ECV. These structural changes lead to worse LV global and segmental diastolic function and in turn reduced exercise tolerance.

Examining the impact of inducible ischemia on myocardial fibrosis and exercise capacity in hypertrophic cardiomyopathy

“…The ECG triggered modified Look Locker inversion recovery (MOLLI) sequence was employed for assessment of myocardial T1 relaxation times in a mid-ventricular slice. Native myocardial T1 relaxation time was measured before administration of contrast 16 . Regadenoson 0.4 mg (Astellas, Northbrook, Illinois, USA) was injected over approximately 10 s into a peripheral vein followed by a 5 mL saline flush.…”

“…LGE imaging was performed ~ 10 min after intravenous injection of the second dose of gadolinium contrast (rest perfusion imaging) using an ECG gated inversion recovery gradient echo sequence in identical locations to the cine images. Scanning parameters included slice thickness of 6 mm, gap 4 mm, voxel size 2.1 × 1.6 × 6 mm, TE = 1.15, and flip angle = 20° 16 . Acquisition scans for post contrast T1 mapping were performed after the standard delayed enhancement acquisition protocol for a mid-ventricular matching slice, approximately 15–20 min after the infusion of the contrast agent.…”

“…Precontrast 5(3)3 and post-contrast 4(1)3(1)2 heart beat sampling schemes were used on the 1.5-T scanner and pre-contrast 5(4)2 and post-contrast 4(1)2(2)2 heart beat sampling schemes on the 3.0-T scanner. Shimming and delta frequency adjustments were applied to minimize off-resonance artifacts 16 .…”

“…The remainder of patients were referrals from other institutions thus echocardiographic studies were not available for analysis. Dynamic LVOT obstruction was quantified at rest, with the Valsalva maneuver, and with exercise if indicated (six patients had exercise echocardiography, and two of them had no LVOT obstruction at rest but provokable LVOT obstruction with exercise echocardiography) 16 . In patients who did not have an echocardiographic study available for analysis within 30 days of CMR, we used CMR findings or available echocardiographic studies outside of the 30 day window, to determine the presence of LVOT obstruction.…”

Electrocardiographic Markers of Fibrosis in Cardiomyopathy: A Beginning of a Long Journey

“…Occurrence of late gadolinium enhancement (LGE) in cMRI, which accurately shows focal fibrotic lesions, has been associated with increased risk for ventricular arrhythmias in both dilated and hypertrophic cardiomyopathy (HCM) [2,3]. Furthermore, cMRI T1 relaxation time seems promising for identifying scattered interstitial fibrosis, which is undetected in LGE imaging, but can potentially cause similar risk for arrhythmias [4]. The only problem is that at the moment, cMRI cannot be considered as a screening tool due to availability and pricing issues.…”