Assessment of Diastolic Function in Hypertrophic Cardiomyopathy by Computed Tomography Derived Analysis of Left Ventricular Filling

Introduction: Hypertrophic cardiomyopathy (HCM) is characterized by abnormal left ventricular (LV) filling, resulting in diastolic dysfunction. Echocardiography is the clinical standard for assessment of diastolic dysfunction, but only modestly correlates with invasively derived LV filling pressures in this condition. Since cardiac computed tomography angiography (CTA) is ideally suited for accurate measurement of simultaneous LV and left atrial (LA) volume changes, we hypothesized that CTA would be useful in the assessment of diastolic function in HCM.

Methods: We studied 21 patients with HCM, age 57±14 previously diagnosed by echocardiography, and 21 age-matched controls with normal diastolic function by echo, who had undergone CTA. Phases were reconstructed every 10% of the cardiac cycle, and end-diastole, end-systole and diastasis identified. From these, LA and LV volumes were calculated and early and late diastolic volume changes derived.

Results: As expected, HCM patients had significantly larger LV mass (108 ± 28g/m² vs. 57 ± 10g/m², p<0.0001) and LA volumes (p<0.001). The HCM group had reduced LA total emptying fraction (30 ± 7% vs. 42 ± 6%, p<0.0001) while conduit volume, which represents LV filling directly from the pulmonary veins, was increased (30 ± 6 ml/m² vs 22 ± 4ml/m², p<0.0001). In fact, conduit volume contributed 60 ± 10% vs. 47 ± 6%, p<0.001) of the total LV diastolic filling, suggesting that passive filling of the LV compensates for LA dysfunction, but at the expense of increased pulmonary filling pressure. In addition, conduit volume correlates strongly with LV mass (r=0.65).

Conclusion: this study suggests that accurate simultaneous depiction of CT-derived LV and LA volume changes throughout the cardiac cycle can characterize diastolic dysfunction in HCM.