ABSTRACT
BACKGROUND: Exercise intolerance is the most common symptom in hypertrophic cardiomyopathy (HCM). We examined whether inability to augment myocardial mechanics during exercise would influence functional performance and clinical outcomes in HCM. METHODS: Ninety-five HCM patients (32 nonobstructive, 32 labile-obstructive, 31 obstructive) and 26 controls of similar age and gender distribution were recruited prospectively. They underwent rest and treadmill stress strain echocardiography, and 61 of them underwent magnetic resonance imaging. Mechanical reserve (MRES) was defined as percent change in systolic strain rate (SR) immediately postexercise. RESULTS: Global strain and SR were significantly lower in HCM patients at rest (strain: nonobstructive, -15.6 ± 3.0; labile-obstructive, -15.9 ± 3.0; obstructive, -13.8 ± 2.9; control, -17.7% ± 2.1%, P < .001; SR: nonobstructive, -0.92 ± 0.20; labile-obstructive, -0.94 ± 0.17; obstructive, -0.85 ± 0.18; control, -1.04 ± 0.14 s-1, P = .002); and immediately postexercise (strain: nonobstructive, -15.6 ± 3.0; labile-obstructive, -17.6 ± 3.6; obstructive, -15.6 ± 3.6; control, -19.2 ± 3.1%; P = .001; SR: nonobstructive, -1.41 ± 0.37; labile-obstructive, -1.64 ± 0.38; obstructive, -1.32 ± 0.29; control, -1.82 ± 0.29 s-1, P < .001). MRES was lower in nonobstructive and obstructive compared with labile-obstructive and controls (51% ± 29%, 54% ± 31%, 78% ± 38%, 77% ± 30%, P = .001, respectively). Postexercise SR and MRES were associated with exercise capacity (r = 0.47 and 0.42, P < .001 both, respectively). When adjusted for age, gender, body mass index, E/e', and resting peak instantaneous systolic gradient, postexercise SR best predicted exercise capacity (r = 0.74, P = .003). Postexercise SR was correlated with extent of late gadolinium enhancement (r = 0.34, P = .03). By Cox regression, exercise SR and MRES predicted ventricular tachycardia/ventricular fibrillation (VT/VF) even after adjustment for age, gender, family history of sudden cardiac death, septum ≥ 3 cm and abnormal blood pressure response (P = .04 and P = .046, respectively). CONCLUSIONS: Nonobstructive and obstructive patients have reduced MRES compared with labile-obstructive and controls. Postexercise SR correlates with LGE and exercise capacity. Exercise SR and MRES predict VT/VF.
Subject(s)
Cardiomyopathy, Hypertrophic/physiopathology , Echocardiography, Stress/methods , Exercise Tolerance/physiology , Heart Ventricles/diagnostic imaging , Rest/physiology , Ventricular Function, Left/physiology , Cardiomyopathy, Hypertrophic/diagnosis , Disease Progression , Female , Follow-Up Studies , Heart Ventricles/physiopathology , Humans , Magnetic Resonance Imaging, Cine/methods , Male , Middle Aged , Prognosis , ROC Curve , Retrospective Studies , SystoleABSTRACT
BACKGROUND: Hypertrophic cardiomyopathy (HCM) is traditionally classified based on a left ventricular outflow tract (LVOT) pressure gradient of 30mmHg at rest or with provocation. There are no data on whether 30mmHg is the most informative cut-off value and whether provoked gradients offer any information regarding outcomes. METHODS: Resting and provoked peak LVOT pressure gradients were measured by Doppler echocardiography in patients fulfilling guidelines criteria for HCM. A composite clinical outcome including new onset atrial fibrillation, ventricular tachycardia/fibrillation, heart failure, transplantation, and death was examined over a median follow-up period of 2.1years. RESULTS: Among 536 patients, 131 patients had resting LVOT gradients greater than 30mmHg. Subjects with higher resting gradients were older with more cardiovascular events. For provoked gradients, a bi-modal risk distribution was found. Patients with provoked gradients >90mmHg (HR 3.92, 95% CI 1.97-7.79) or <30mmHg (HR 2.15, 95% CI 1.08-4.29) have more events compared to those with gradients between 30 and 89mmHg in multivariable analysis. The introduction of two cut-off points for provoked gradients allowed HCM to be reclassified into four groups: patients with "benign" latent HCM (provoked gradient 30-89mmHg) had the best prognosis, whereas those with persistent obstructive HCM had the worst outcome. CONCLUSIONS: Provoked LVOT pressure gradients offer additional information regarding clinical outcomes in HCM. Applying cut-off points at 30 and 90mmHg to provoked LVOT pressure gradients further classifies HCM patients into low-, intermediate- and high-risk groups.
