Cardiomyocyte functions couple with left ventricular geometric patterns in hypertension.
Previous studies have suggested the prognostic significance of left ventricular (LV) geometric patterns in essential hypertension. However, the relation between cardiomyocyte functional changes and LV geometric patterns has not been clarified. This study was designed to assess the morphological and functional changes in isolated myocytes derived from different LV geometric patterns in hypertension. After 2-3 weeks of a high-salt (8%) diet from the age of 6 weeks, 20 Dahl salt-sensitive (DS) rats were classified into the following three groups on the basis of an echocardiographically determined LV mass index and the relative wall thickness: concentric hypertrophy (11), eccentric hypertrophy (4), and concentric remodeling (5). Ten Dahl salt-resistant (DR) rats served as controls. In vivo LV functions were assessed based on echocardiographic measurements. We examined ventricular myocytes isolated from all groups. To evaluate the force-frequency relation, cardiomyocytes isolated from all groups were paced at stimulation rates of 0.3, 0.5, 1.0, 2.0, and 3.0 Hz. Concentric hypertrophy and eccentric hypertrophy groups exhibited an increase in myocyte width but no changes in the length. Concentric hypertrophy and concentric remodeling groups demonstrated in vivo LV dysfunction. In addition, DS rats, especially these with concentric hypertrophy, demonstrated impaired frequency responses in terms of both myocyte contraction and relaxation compared with DR rats. This impaired force-frequency relationship was especially remarkable at high frequencies. These findings suggest that the structural and functional changes in cardiomyocytes are closely related to the LV geometric pattern and may contribute to a different prognosis according to different geometric patterns.
Ohtsuka
T
T
Second Department of Internal Medicine, Ehime University School of Medicine, Japan.
Suzuki
M
M
Hamada
M
M
Hiwada
K
K
D000818:Animals; D004558:Electric Stimulation; D006321:Heart / Q000503:physiopathology*; D006439:Hemodynamics; D006973:Hypertension / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D009200:Myocardial Contraction; D009206:Myocardium / Q000473:pathology; D051381:Rats; D020303:Rats, Inbred Dahl; D016277:Ventricular Function, Left