Ventricular failure and cellular remodeling with chronic supraventricular tachycardia

Chronic supraventricular tachycardia has been associated with ventricular dysfunction in human beings and in animals. The changes in ventricular size and shape and the myocyte remodeling that may occur with chronic supraventricular tachycardia are unknown. Left and right ventricular remodeling and myocyte changes were examined in 12 pigs after 3 weeks of atrial pacing (supraventricular tachycardia at 240 beats/min and in 10 control pigs (105 +/- 3 beats/min). Chronic supraventricular tachycardia resulted in decreased left ventricular and right ventricular ejection fractions compared with control values (left ventricle, 26% +/- 4% versus 60% +/- 1%; right ventricle, 19% +/- 3% versus 53% +/- 3%; p less than 0.05 for both), decreased wall thickness (left ventricle, 8.3 +/- 0.1 mm versus 10.5 +/- 0.2 mm; right ventricle, 2.8 +/- 0.3 mm versus 4.2 +/- 0.2 mm; p less than 0.05 for both), and increased end-diastolic volumes (left ventricle, 66 +/- 10 ml versus 54 +/- 4 ml; right ventricle, 78 +/- 8 ml versus 56 +/- 4 ml; p less than 0.05 for both). Myocardial water content was significantly higher with supraventricular tachycardia than in control pigs (left ventricle, 82% +/- 4% versus 76% +/- 4%; right ventricle, 83% +/- 4% versus 78% +/- 2%; p less than 0.05 for both). According to computer-aided stereological studies, the percent volume of myocytes in the subendocardial layer of the hearts that underwent supraventricular tachycardia was smaller than that of the control hearts (left ventricle, 62% +/- 2% versus 79% +/- 1%; right ventricle, 55% +/- 4% versus 77% +/- 1%; p less than 0.05 for both) and myocyte diameter was reduced (left ventricle, 16 +/- 1 microns versus 23 +/- 2 microns; right ventricle, 13 +/- 1 microns versus 22 +/- 2 microns; p less than 0.05 for both). Further, myocytes isolated from the left ventricles of the group with supraventricular tachycardia were significantly longer than were control myocytes (190 +/- 25 microns versus 145 +/- 30 microns, p less than 0.05 for both). In summary, chronic supraventricular tachycardia caused significant right and left ventricular failure, with a reduction in wall thickness and chamber dilatation. This was accompanied by a reduction in the percent volume of myocytes occupying the subendocardial layer, with reduced myocyte diameter and increased myocyte length and water content. These changes are likely to be important in understanding supraventricular tachycardia-induced ventricular dysfunction.