Pathophysiologic significance of left ventricular hypertrophy in dilated cardiomyopathy
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K Iida1, M el Sersi, K Fujieda
1Department of Internal Medicine, University of Tsukuba, Japan.
Insights
Patients with dilated cardiomyopathy and left ventricular hypertrophy show improved systolic reserve and require less norepinephrine during exercise. This suggests a mechanism for their better prognosis in DCM.
Area of Science:
- Cardiology
- Cardiovascular Physiology
- Heart Failure Research
Background:
- Dilated cardiomyopathy (DCM) patients with left ventricular hypertrophy (LVH) exhibit a better prognosis.
- The underlying pathophysiological mechanisms for this improved outcome remain unclear.
Purpose of the Study:
- To investigate the pathophysiological significance of LVH in DCM.
- To clarify why LVH is associated with a better prognosis in DCM patients.
Main Methods:
- Isoproterenol infusion echocardiography was performed in 17 DCM patients.
- Plasma epinephrine and norepinephrine levels were measured at rest and during exercise.
- Patients were categorized into LVH-positive (LVH+) and LVH-negative (LVH-) groups based on ventricular wall thickness.
Main Results:
- Fractional shortening response to isoproterenol was significantly higher in the LVH+ group compared to the LVH- group.
- Plasma norepinephrine levels at peak exercise were significantly lower in the LVH+ group than in the LVH- group.
- No significant difference in resting fractional shortening or plasma norepinephrine levels was observed between groups.
Conclusions:
- Patients with DCM and LVH possess greater systolic reserve, indicated by a superior response to isoproterenol.
- Lower plasma norepinephrine levels are sufficient to activate the myocardium during exercise in DCM patients with LVH.
- These findings suggest that enhanced systolic reserve and altered catecholamine response in LVH+ DCM patients contribute to their better clinical prognosis.
Background And Hypothesis:
Patients with dilated cardiomyopathy (DCM) with left ventricular hypertrophy (LVH) have been found to have a better prognosis than patients without LVH. However, the pathophysiologic mechanism for that has not been investigated. We sought to clarify the pathophysiologic significance of LVH in DCM.
Methods:
We performed isoproterenol infusion echocardiography (0.02 micrograms/kg/min) in 17 patients with DCM, and measured plasma epinephrine and norepinephrine levels at rest and at the end of ergometer exercise in 14 of the 17 patients. Patients were classified into groups according to the presence (9 patients) (LVH+) or absence (8 patients) (LVH-) of LVH. Left ventricular hypertrophy was defined as an inter-ventricular thickness or posterior wall thickness > or = 13 mm.
Results:
Although there was no significant difference between groups in fractional shortening at rest during isoproterenol infusion, fractional shortening was significantly higher in the LVH(+) group than in the LVH(-) group (29 +/- 9 vs. 17 +/- 8%; p < 0.025). Although there was no significant difference in plasma norepinephrine level, it was significantly lower in the LVH(+) group than in the LVH(-) group (233 +/- 169 vs. 519 +/- 258 pg/ml; p < 0.05) at the end point of the exercise.
Conclusion:
Systolic reserve, represented by the response to isoproterenol, is greater in patients with DCM with LVH than in those without LVH, and a lower plasma level of norepinephrine is needed to activate the myocardium during exercise in patients with DCM with LVH. This pathophysiologic characteristic could be one of the mechanisms which explain a better prognosis in patients with DCM with LVH.
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