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Echocardiographic and Doppler flow observations in obstructed and nonobstructed hypertrophic cardiomyopathy
Insights
Hypertrophic cardiomyopathy (HC) with an outflow gradient prolongs ejection time and alters aortic flow velocity. Obstructed HC shows midsystolic deceleration and mitral regurgitation, challenging early emptying theories.
Area of Science:
- Cardiology
- Echocardiography
- Cardiovascular Physiology
Background:
- Investigational theories suggest left ventricular (LV) ejection in hypertrophic cardiomyopathy (HC) concludes early due to rapid emptying, not obstruction.
- This hypothesis posits that LV ejection is not impeded but merely shortened in HC, irrespective of outflow gradient presence.
Purpose of the Study:
- To investigate the timing and pattern of left ventricular (LV) ejection in hypertrophic cardiomyopathy (HC) patients.
- To differentiate between early LV emptying and outflow obstruction as the primary mechanism in HC using Doppler echocardiography.
Main Methods:
- Pulsed Doppler echocardiography was used to record ascending aortic flow velocity patterns.
- Twenty HC patients (12 obstructed, 8 nonobstructed) and 20 normal subjects were studied.
- Doppler left atrial flow velocity recordings were obtained in a subset of patients.
Main Results:
- Peak aortic flow velocity was similar across all groups (obstructed HC, nonobstructed HC, normal subjects).
- Mean ejection time was significantly longer in obstructed HC patients compared to nonobstructed HC and normal subjects.
- A characteristic midsystolic deceleration in aortic flow velocity was observed in most obstructed HC patients, alongside mitral regurgitation in some.
Conclusions:
- Left ventricular (LV) ejection time is prolonged in hypertrophic cardiomyopathy (HC) with an outflow gradient.
- The observed aortic flow velocity patterns and mitral regurgitation in obstructed HC suggest outflow impediment rather than simply early LV emptying.
- Doppler echocardiography effectively differentiates these mechanisms in hypertrophic cardiomyopathy (HC).
Abstract:
Some investigators have suggested that left ventricular (LV) ejection is completed much earlier than normal in patients with hypertrophic cardiomyopathy (HC), whether or not a LV outflow gradient is present, and they have therefore concluded that LV ejection is not impeded in HC, but merely ends early because of early completion of LV emptying. This possibility was examined using pulsed Doppler echocardiography to record ascending aortic flow velocity patterns in 20 patients with HC, 12 with evidence of LV outflow gradient at rest (obstructed HC) and 8 without evidence of a significant resting gradient (nonobstructed HC). Peak aortic flow velocity was similar in patients with nonobstructed HC (92 +/- 26 cm/s) and those with obstructed HC (94 +/- 26 cm/s) and in 20 normal subjects (92 +/- 11 cm/s). However, mean ejection time measured from the aortic flow velocity tracing or aortic echogram was longer in those with obstructed HC (345 +/- 30 ms) than in those with nonobstructed HC (296 +/- 24 ms, p less than 0.02) and in normal subjects (294 +/- 19 ms, p less than 0.01). Furthermore, a rapid decrease in aortic flow velocity in midsystole was seen in 11 of 12 patients with obstructed HC, but in none of the patients with nonobstructed HC or normal subjects. Doppler left atrial flow velocity recordings, obtained in 11 patients, demonstrated mitral regurgitation in 4 of 5 patients with obstructed HC but in none of 6 patients with nonobstructed HC.(ABSTRACT TRUNCATED AT 250 WORDS)