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Relation between myocardial beta-adrenergic receptor and left ventricular function in patients with left ventricular
N Sakagoshi1, S Nakano, K Taniguchi
11st Department of Surgery, Osaka University School of Medicine, Japan.
Insights
In patients with chronic mitral regurgitation, reduced myocardial beta-adrenergic receptor density is linked to worsening heart failure and impaired left ventricular (LV) contractile function. This suggests receptor down-regulation contributes to LV dysfunction.
Area of Science:
- Cardiology
- Molecular Cardiology
Background:
- Myocardial beta-adrenergic receptors play a crucial role in regulating left ventricular (LV) function.
- Chronic mitral regurgitation can lead to LV volume overload and dysfunction.
- Understanding the relationship between these receptors and LV function in this condition is important for patient management.
Purpose of the Study:
- To investigate the association between myocardial beta-adrenergic receptor density and left ventricular (LV) function in patients with chronic mitral regurgitation.
- To explore the correlation between receptor density and the severity of heart failure and contractile state.
Main Methods:
- Studied 10 patients with chronic mitral regurgitation undergoing mitral valve replacement.
- Assessed beta-adrenergic receptor density in LV papillary muscle membranes.
- Evaluated cardiac function using preoperative cardiac catheterization, including New York Heart Association (NYHA) classification and end-systolic stress/end-systolic volume index ratio.
Main Results:
- Beta-adrenergic receptor density was significantly higher in patients with NYHA class II/III heart failure compared to class IV (59 +/- 19 vs 37 +/- 3 fmol/mg protein, p < 0.05).
- A positive correlation was observed between beta-adrenergic receptor density and the end-systolic stress/end-systolic volume index ratio (p < 0.005), an indicator of contractile function.
- No significant correlation was found between receptor density and cardiac index, pulmonary artery wedge pressure, or LV ejection fraction.
Conclusions:
- Decreased myocardial beta-adrenergic receptor density is associated with increased symptoms and LV dysfunction, particularly impaired contractility, in patients with chronic mitral regurgitation.
- This reduction may be due to receptor down-regulation, contributing to the progression of heart failure.
- The findings highlight the importance of beta-adrenergic receptor status in the pathophysiology of LV dysfunction in this patient population.
Abstract:
The relation between myocardial beta-adrenergic receptor and left ventricular (LV) function was studied in 10 patients, aged 41 to 61 years (average 51), with LV volume overload mainly due to chronic mitral regurgitation. Beta-adrenergic receptors were examined using crude membrane in LV papillary muscle obtained at mitral valve replacement. Cardiac function was evaluated at preoperative cardiac catheterization with the interval to surgery of 1 to 33 months (average 7). Beta-adrenergic receptor density in 7 patients with New York Heart Association class II or III congestive heart failure was higher than that in 3 patients with class IV heart failure (59 +/- 19 vs 37 +/- 3 fmol/mg protein, p less than 0.05). Beta-adrenergic receptor density showed a positive correlation with end-systolic stress/end-systolic volume index ratio, the index for contractile function (p less than 0.005). Other parameters such as cardiac index, pulmonary artery wedge pressure and LV ejection fraction had no significant correlation to beta-adrenergic receptor. The results demonstrated that increases in symptom and LV dysfunction, particularly of the contractile state, was associated with decreased myocardial beta-adrenergic receptor density from possible down-regulation in patients with chronic mitral regurgitation with or without aortic regurgitation.