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[Evaluation of norepinephrine content in the myocardium in hypertensive patients with left ventricular hypertrophy]
C Schwebel1, D Fagret, F Tremel
1Service de médecine interne et cardiologie, CHRU, BP 217, Grenoble.
Insights
This study found that myocardial scintigraphy using 123I-meta-iodobenzylguanidine can assess cardiac norepinephrine levels in essential hypertension patients with left ventricular hypertrophy, revealing normal or high uptake.
Area of Science:
- Cardiology
- Nuclear Medicine
- Hypertension Research
Background:
- Sympathetic nervous system activity is implicated in hypertension and left ventricular hypertrophy.
- Assessing cardiac norepinephrine levels is crucial for understanding these conditions.
Purpose of the Study:
- To estimate myocardial norepinephrine content in essential hypertensive patients with left ventricular hypertrophy.
- To evaluate the utility of 123I-meta-iodobenzylguanidine scintigraphy for this assessment.
Main Methods:
- Eight hypertensive patients with left ventricular hypertrophy underwent blood pressure monitoring and echocardiography.
- Cardiac and mediastinal radioactivity was measured 4 hours after injecting 123I-meta-iodobenzylguanidine.
- Myocardial uptake was calculated as the cardiac/mediastinal ratio.
Main Results:
- Meta-iodobenzylguanidine myocardial uptake in hypertensive patients was comparable to controls (1.89 +/- 0.19 vs. 1.78 +/- 0.19).
- A significant correlation was observed between uptake and effort systolic blood pressure variation and heart rate increase.
- No correlation was found with left ventricular mass index or ambulatory blood pressure.
Conclusions:
- Myocardial scintigraphy with 123I-meta-iodobenzylguanidine can effectively measure cardiac norepinephrine content in humans.
- Uptake levels were normal or high in hypertensive patients with left ventricular hypertrophy, aligning with experimental models.
Abstract:
The sympathetic nervous system seems to be a non hemodynamic factor involved in the development of hypertension and in left ventricular hypertrophy determinism. The aim of this study was to estimate the myocardial norepinephrine content in essential hypertensive patients, using a reliable radio-iodinated marker of norepinephrine: the 123I-meta-iodobenzylguanidine (123I-meta-iodobenzylguanidine). Eight male and female hypertensive patients with left ventricular hypertrophy and average age of 52 +/- 9 years underwent a resting, ambulatory and effort blood pressure measure. Echocardiographic parameters allowed measure of left ventricular mass index (according to Devereux, and we considered left ventricular hypertrophy as left ventricular mass index greater than 120g/m2. Plasma norepinephrine is measured at rest. Cardiac and mediastinal radioactivity is detected 4 h after a 4mCi i.v. injection of 123I-meta-iodobenzylguanidine and meta-iodobenzylguanidine myocardial uptake is definite as the cardiac/mediastinal ratio (N:1.78 +/- 0.19). Meta-iodobenzylguanidine-myocardial uptake average value of hypertensive patients was 1.89 +/- 0.19 (1.63 to 2.25) without statistical difference to control subjects. We found a significative correlation between meta-iodobenzylguanidine myocardial uptake and effort systolic blood pressure variation in one hand, and with heart rate increase with effort in the other hand. There is no correlation between meta-iodobenzylguanidine-myocardial uptake and left ventricular mass index or ambulatory blood pressure. In hypertensive patients with left ventricular hypertrophy, meta-iodobenzylguanidine myocardial uptake is normal or high, in agreement with experimental data in SHRs, model of human essential hypertension. Therefore myocardial scintigraphy with 123I-meta-iodobenzylguanidine can appreciate cardiac norepinephrine content in humans.