Doppler echocardiography underestimates the prevalence and magnitude of mid‐cavity obstruction in patients with symptomatic hypertrophic cardiomyopathy

OBJECTIVES: To evaluate utility of Doppler echocardiography in the assessment of left ventricular (LV) mid-cavity obstructive (LVMCO) hypertrophic cardiomyopathy (HCM). BACKGROUND: LVMCO is a relatively under-diagnosed complication of HCM and may occur alone or in combination with LV outflow tract obstruction (LVOTO). Identifying and quantifying LVMCO and differentiating it from LVOTO has important implications for patient management. We aimed to assess diagnostic performance of Doppler echocardiography in the assessment of suspected LV obstruction. METHODS: Forty symptomatic HCM patients with suspected obstruction underwent cardiac catheterization, and comparison of location and magnitude of Doppler derived gradients with synchronous invasive measurements (reference standard), at rest and isoprenaline stress (IS). RESULTS: Doppler's diagnostic accuracy for any obstruction (≥30 mmHg) in this cohort was 75% with false positive and false negative rates of 2.5 and 22.5%, respectively. During subanalysis, Doppler's diagnostic accuracy for isolated LVOTO in this selected cohort is 83% with false positive and false negative rates of 4 and 12.5%, respectively. For LVMCO, the accuracy is only 50%, with false positive and false negative rates of 10 and 40%, respectively. Doppler gradients for isolated LVOTO were similar to invasive: 85 ± 51 and 87 ± 35 mmHg, respectively (P = 0.77). Doppler gradients in LVMCO were consistently lower than invasive: 45 ± 38 and 81 ± 31 mmHg, respectively (P = 0.0002). Mid-systolic flow cessation and/or contamination of spectral signals were identified as causes of Doppler-derived inaccuracies. CONCLUSIONS: Doppler echocardiography under-diagnoses and underestimates severity of LVMCO in symptomatic HCM patients. Recognition of abrupt mid-systolic flow cessation and invasive measurements may improve detection of LVMCO in HCM.