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Causal relation between the pressure gradient and left ventricular ejection time in hypertrophic cardiomyopathy
Z Sasson1, M Henderson, S Wilansky
1Division of Cardiology, Toronto General Hospital, University of Toronto, Ontario, Canada.
Insights
In hypertrophic obstructive cardiomyopathy, left ventricular ejection time directly correlates with the severity of left ventricular outflow obstruction. This relationship is significant, even after heart rate correction, but shows interpatient variability.
Area of Science:
- Cardiology
- Cardiovascular Physiology
Background:
- Hypertrophic obstructive cardiomyopathy (HOCM) is characterized by left ventricular outflow tract (LVOT) obstruction.
- Understanding the relationship between LVOT obstruction severity and cardiac function is crucial for patient management.
Purpose of the Study:
- To evaluate the direct relationship between the pressure gradient across the LVOT and left ventricular ejection time (LVET) in patients with HOCM.
Main Methods:
- Dual catheterization was used to measure LVOT pressure gradients and LVET in 10 HOCM patients.
- Pharmacological agents were used to alter the pressure gradient.
- Constant atrial pacing was employed to eliminate heart rate variability.
Main Results:
- A strong, direct linear correlation was observed between LVET and the pressure gradient in individual patients (mean r=0.97).
- Changes in pressure gradient magnitude directly corresponded to changes in LVET (mean r=0.98).
- Pooled data analysis using heart rate correction showed a significant but weaker correlation (r=0.86) due to interpatient variability.
Conclusions:
- A clear, direct, and significant relationship exists between LVOT pressure gradient severity and LVET in HOCM.
- Interpatient variability in factors like myocardial contractility influences the corrected LVET-gradient relationship.
Abstract:
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 greater than or equal to 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.(ABSTRACT TRUNCATED AT 250 WORDS)