Variability of Left Ventricular Outflow Tract Gradient During Cardiac Catheterization in Patients With Hypertrophic Cardiomyopathy

Study Questions:

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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