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Effect of Septal Ablation on Myocardial Relaxation and Left Atrial Pressure in Hypertrophic Cardiomyopathy

An Invasive Hemodynamic Study

Division of Cardiovascular Diseases and Internal Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota

^_* Reprint requests and correspondence: Dr. Rick A. Nishimura, 200 1st Street SW, Rochester, Minnesota 55906 (Email: rick.nishimura{at}mayo.edu).

Objectives: The objective of this study was to examine the effects of septal ablation on diastolic function with the use of invasive hemodynamics.

Background: Septal ablation is an alternative therapy for patients with obstructive hypertrophic cardiomyopathy (HCM). However, its beneficial effect on diastolic function, by relieving the systolic contraction load, may be countered by adverse effects from the infarction on left ventricular mechanics.

Methods: Using high-fidelity, micromanometer-tipped catheters, we examined 40 HCM patients by taking direct measurements of the left ventricular outflow tract (LVOT) gradient, time constant of myocardial relaxation (tau), and left atrial pressure (LAP) before and after septal ablation.

Results: Although there was an overall reduction in LVOT gradient, septal ablation resulted in variable changes in myocardial relaxation and left atrial pressure. In 20 patients (50%), LAP increased. The magnitude of LVOT gradient reduction directly correlated with the effects of septal ablation on LAP (R = 0.58; p < 0.0001). Those patients with a greater decrease in the LVOT gradient had better improvement in direct LAP. Furthermore, those patients with a larger decrease in left ventricular outflow tract gradient had a beneficial enhancement of ventricular relaxation, as measured by tau (R = 0.43; p = 0.006). Thus, the beneficial enhancement of relaxation was directly related to improvement in LAP (R = 0.75; p < 0.0001).

Conclusions: Septal ablation results in variable effects on left ventricular filling pressure, which are dependent upon the magnitude of reduction in the LVOT gradient. These effects are mediated in part by effects of ablation on myocardial relaxation. These findings shed insight into the pathophysiologic effects of septal reduction therapy in patients with HCM.

Key Words: hypertrophic cardiomyopathy • septal ablation • diastole

Abbreviations and Acronyms   EDP = end-diastolic pressure   HCM = hypertrophic cardiomyopathy   LAP = left atrial pressure   LV = left ventricle   LVOT = left ventricular outflow tract   tau = time constant of myocardial relaxation