Author + information
- Received June 6, 1988
- Revision received October 11, 1988
- Accepted December 14, 1988
- Published online May 1, 1989.
- Zion Sasson, MD, FACC∗,
- Mark Henderson, MD,
- Susan Wilansky, MD,
- Harry Rakowski, MD and
- E.Douglas Wigle, MD, FACC
- ↵∗Address for reprints: Zion Sasson, MD. Division of Cardiology. The Wellesley Hospital. 160 Wellesley Street East. Toronto, Ontario. Canada M4YIJ3.
This study was designed to evaluate the relation between severity of obstruction to left ventricular outflow and left ventricular ejection time in hypertrophic obstructive cardiomyopathy. With dual catheters across the left ventricular outflow tract, the pressure gradient and corresponding left ventricular ejection time were measured in 10 patients as the pressure gradient was pharmacologically provoked or abolished, or both. The patients were studied during constant atrial pacing to avoid the potential errors introduced with heart rate correction equations.
The pressure gradient was pharmacologically provoked or reduced over a range of ≥62 mm Hg per patient. In each patient the left ventricular ejection time varied directly with the pressure gradient (mean r = 0.97, range 0.92 to 1.00). The change in magnitude of the pressure gradient varied directly with the corresponding change in the measured ejection time (mean r = 0.98, range 0.97 to 1.00).
When the data from all 10 patients were pooled with use of Weissler's heart rate correction equation, the relation between the corrected left ventricular ejection time and the pressure gradient was still significant and linear (r = 0.86), but less so than in individual patients. This difference was the result of marked interpatient variability in the slope of this linear relation reflecting interpatient differences in other important factors, such as underlying myocardial contractility and stroke volume, that influence left ventricular ejection time.
This study demonstrates a clear, direct and highly significant relation between the magnitude of the pressure gradient and the left ventricular ejection time in hypertrophic obstructive cardiomyopathy. These findings suggest a causal relation between the pressure gradient and ejection time and support the concept that the pressure gradient in this condition represents a true mechanical impediment to left ventricular outflow.
☆ This study was supported in part by grants from the Canadian Heart Foundation. Ottawa. Ontario and the Heart and Stroke Foundation of Ontario. Toronto.
- Received June 6, 1988.
- Revision received October 11, 1988.
- Accepted December 14, 1988.