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Muscle dynamics in hypertrophic cardiomyopathy
Insights
Patients with hypertrophic cardiomyopathy (HCM) show varied isovolumic relaxation periods (IRP). A subset with short IRP may indicate outflow tract obstruction, challenging IRP
Area of Science:
- Cardiology
- Cardiovascular Physiology
- Echocardiography
Background:
- Hypertrophic cardiomyopathy (HCM) is often associated with prolonged isovolumic relaxation period (IRP), indicating impaired left ventricular pressure decline.
- Previous studies suggest IRP is a key indicator of diastolic dysfunction in HCM.
Purpose of the Study:
- To investigate the variability of IRP in a cohort of hypertrophic cardiomyopathy patients.
- To identify subgroups within HCM patients based on IRP measurements.
- To explore the relationship between short IRP and hemodynamic characteristics, including outflow tract obstruction.
Main Methods:
- Simultaneous recordings of echocardiogram, apexcardiogram, phonocardiogram, and ECG were performed.
- Eighty-four patients with proven HCM and 31 normal subjects were studied.
- Isovolumic relaxation period (IRP) was measured and analyzed across different subgroups.
Main Results:
- Normal subjects had a mean IRP of 61 ± 11 ms.
- HCM patients exhibited a wide range of IRP values (0–160 ms).
- Three subgroups were identified: prolonged IRP (sinus rhythm), normal IRP (atrial fibrillation), and short IRP (0–45 ms).
- The short IRP subgroup showed signs of outflow tract systolic pressure gradient, aortic valve abnormalities, and mitral valve motion abnormalities.
- Short IRP was linked to delayed aortic valve closure, questioning the reliability of the A2-Mo interval as a measure of ventricular relaxation.
Conclusions:
- Isovolumic relaxation period (IRP) shows significant variability in hypertrophic cardiomyopathy (HCM).
- A subset of HCM patients with short IRP may present with dynamic outflow tract obstruction.
- The non-invasive A2-Mo interval may not consistently reflect left ventricular relaxation in all HCM patients, especially those with short IRP.
Abstract:
Previous reports have demonstrated that patients with hypertrophic cardiomyopathy (HCM) have prolonged isovolumic relaxation period (IRP) reflecting reduced rate of fall of left ventricular pressure. Eighty four patients with proven hypertrophic cardiomyopathy and 31 normal subjects were studied by simultaneous recordings of echocardiogram, apexcardiogram, phonocardiogram and ECG. In normal subjects the IRP value was 61 +/- 11 ms (mean +/- s.d.). In the 84 patients there was enormous variability of the IRP value from 0 to 160 ms reflecting abnormal and incoordinate (but not necessarily impaired) relaxation and it was possible to identify three subgroups among the patients: 60 patients in sinus rhythm who had prolonged IRP and significantly above the normal values, 9 patients in atrial fibrillation in whom the IRP was within the normal range and 15 patients with IRP values between 0-45 ms, with the mean (26 ms) below the normal range (mean +/- 2 s.d.). This group of patients with short IRP also had signs of outflow tract systolic pressure gradient, with partial mid-systolic closure of the aortic valve, systolic anterior motion of the anterior mitral valve leaflet and paradoxical splitting of the second heart sound. It is suggested that the short IRP is due to extremely delayed aortic valve closure and careful scrutiny of this subset with haemodynamic evaluation has shown that this non-invasive interval (A2-Mo) may not always be a valid measure of left ventricular relaxation.