Variability of Left Ventricular Outflow Tract Gradient During Cardiac Catheterization in Patients With Hypertrophic Cardiomyopathy
What is the variability of left ventricular outflow tract (LVOT) gradients in patients with hypertrophic cardiomyopathy (HCM) during cardiac catheterization?
A cohort of 50 symptomatic patients with HCM (mean age 55 ± 15 years; 48% men) underwent cardiac catheterization with high-fidelity, micromanometer-tip catheters and trans-septal measurement of LV pressures. Obstruction was defined as resting LVOT gradient ≥30 mm Hg and severe obstruction as ≥50 mm Hg. Variability in LVOT gradient was calculated as the difference of the largest and smallest LVOT gradients in the absence of provocative maneuvers or interventions.
The largest LVOT gradient was 54.6 ± 56.4 mm Hg. The spontaneous variability in LVOT gradient was 49.0 ± 53.1 mm Hg (range 0-210.8 mm Hg, median 15 mm Hg). Discrepant classification of resting LVOT gradient severity was possible in 25 patients (50%). Twenty patients (40%) with severe obstruction could have been misclassified with regard to obstruction severity.
In patients with HCM, the LVOT gradient fluctuates significantly during a single hemodynamic assessment. Spontaneous variability could lead to misclassification of obstruction severity in one-half of studied patients. The dynamic nature of LVOT obstruction must be considered when assessing resting hemodynamics or the success of a given intervention during cardiac catheterization.
This invasive hemodynamic study of LVOT peak-to-peak gradients among patients with HCM revealed substantial respiratory, beat-to-beat, and spontaneous variability. Presumably this is due to gradient generation caused by a dynamic rather than a fixed obstruction. These data suggest that provocative maneuvers should be performed in conjunction with invasive or noninvasive testing among patients with HCM before concluding that obstruction is absent.
Clinical Topics: Heart Failure and Cardiomyopathies
Keywords: Ventricular Outflow Obstruction, Cardiology, Cardiomyopathy, Hypertrophic, Cardiac Catheterization, Hemodynamics
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