Timing and Significance of Exercise-Induced Left Ventricular Outflow Tract Pressure Gradients in Hypertrophic Cardiomyopathy

Abstract

The relation of exercise-induced left ventricular (LV) outflow tract obstruction to functional capacity in hypertrophic cardiomyopathy (HC) is incompletely defined. Thus, we assessed the patterns of onset of physiologically provoked LV outflow gradients and exercise performance in 74 consecutive patients with HC (age 45 ± 16 years; 74% men) without LV outflow obstruction at rest. The subaortic gradients were measured serially using echocardiography in these 74 patients during maximum, symptom-limited, upright bicycle exercise testing. The time course of the provoked gradients and the relation to exercise performance were assessed. Of the 74 patients, 30 (41%) developed a dynamic LV outflow gradient of ≥30 mm Hg (mean 78 ± 37 mm Hg) during upright exercise testing that correlated highly with the gradients measured with the patients supine during the immediate recovery period (R² = 0.97). The 16 patients in whom outflow obstruction developed rapidly at low exercise levels (≤5 METs) had a significantly reduced exercise capacity (6.1 ± 1.3 vs 8.0 ± 1.6 METs; p <0.01) compared to the other 14 patients in whom obstruction appeared later at greater exercise levels of >5 METs. The timing of the gradient onset was not predictable from the baseline clinical and echocardiographic features, peak exercise LV outflow tract gradient, or symptoms. In conclusion, in patients with HC without outflow obstruction at rest, the earlier onset of LV outflow tract gradients during physiologic exercise was associated with impaired exercise performance. These findings have provided insights into the determinants of functional impairment in HC and support the potential value of exercise echocardiography in the clinical assessment of patients with HC.

Echocardiography in Hypertrophic Cardiomyopathy: In with Strain, Out with Straining?

“…In contrast, when simultaneous echocardiographic imaging was performed on patients who underwent upright stationary bicycle testing, there was a very high correlation between the provocable LVOT gradient obtained during peak upright exercise and the LVOT gradient in the immediate postexercise supine position. 36 Other relevant studies of upright bicycle exercise involving patients with HCM are summarized in Table 1. 37,38 There are caveats to mention when evaluating patients for exercise-induced LVOTobstruction, regardless of the type of exercise.…”

Diagnosis and management of hypertrophic cardiomyopathy

“…The incidence and severity of exercise-induced LVOT can be increased in post-prandial tests (63) . A study has demonstrated that early development of obstruction is associated with higher reduction in the function capacity (64) . Another study has shown a progressive increase in the LVOT gradient by a range of physiologic manoeuvres: from standing to Valsalva to exercise (65) .…”

O diagnóstico da obstrução da via de saída do ventrículo esquerdo na cardiomiopatia hipertrófica

“…Consecutive measurements under baseline conditions in supine and orthostatic position, and after, at the peak of the exercise and on the recovery phase in orthostatism showed a continuous elevation of the gradient 45 . In a later study, the peak of exercise gradient was demonstrated to present correlation with that on the supine recovery phase, and that the early development of obstruction was associated to higher reduction of function capacity 46 . In other set of cases, although elevation of gradient in 76% of the patients in standing position has been observed, a higher increment was found in exertion, in measurements made in supine recovery phase 40 .…”