Effects of pre-existing left ventricular hypertrophy on ventricular dysfunction and remodeling following myocardial infarction in rats

Diastolic Dysfunction After an Acute Myocardial Infarction in Patients with Antecedent Hypertension

OBJECTIVE

We sought to assess changes in the left ventricular systolic and diastolic function in patients with antecedent hypertension and an acute myocardial infarction.

METHODS

A group of 38 patients with antecedent hypertension and acute myocardial infarction were compared with an age-matched nonhypertensive control group. There was a 30-day follow-up. Outcome measures were left ventricular volumes and ejection fraction, systolic velocities, and strain. Diastolic function was assessed by mitral inflow combined with tissue velocities of the mitral ring.

RESULTS

Patients with antecedent hypertension did not experience any regression in the E/E' ratio (16.5 +/- 7.5 vs 17.1 +/- 9.0, P = not significant) or increase in the E'/A' ratio (0.76 +/- 0.5 vs 0.84 +/- 0.6, P = not significant) compared with significant improvements in E/E' ratio (18.9 +/- 8.7 vs 12.8 +/- 7.4, P < .01) and E'/A' ratio (0.76 +/- 0.5 vs 1.1 +/- 0.7, P < .01) in the control group. This was found despite similar changes ejection fraction, volumes, and systolic strain.

CONCLUSIONS

Patients with antecedent hypertension have incomplete improvement of the diastolic function compared with control subjects despite comparable left ventricular volumes and ejection fraction after an acute myocardial infarction.

Susceptibility to systolic dysfunction in the myocardium from chronically infarcted spontaneously hypertensive rats

We explored whether the hypertensive heart is susceptible to myocardial dysfunction in viable noninfarcted tissue post-myocardial infarction (MI), the potential mechanisms thereof, and the impact of these changes on pump function. Six to seven months after the ligation of the left anterior descending coronary artery, left ventricular (LV) myocardial systolic function, as assessed from the percent shortening of the noninfarcted lateral wall segmental length determined over a range of filling pressures (ultrasonic transducers placed in the lateral wall in anaesthetized, open-chest, ventilated rats) and the percent thickening of the posterior wall (echocardiography), was reduced in infarcted spontaneous hypertensive rats (SHR-MI) ( P < 0.05) but not in normotensive Wistar-Kyoto (WKY-MI) animals compared with corresponding controls [SHR-sham operations (Sham) and WKY-Sham]. This change in the regional myocardial function in SHR-MI, but not in WKY-MI, occurred despite a similar degree of LV dilatation (increased LV end-diastolic dimensions and volume intercept of the LV end-diastolic pressure-volume relation) in SHR-MI and WKY-MI rats and a lack of difference in LV relative wall thinning, LV wall stress, apoptosis [terminal deoxynucleotidyl transferase biotin-dUTP nick-end labeling (TUNEL)], or necrosis (pathological score) between SHR-MI and WKY-MI rats. Although the change in regional myocardial function in the SHR-MI group was not associated with a greater reduction in baseline global LV chamber systolic function [end-systolic elastance (LV Ees) and endocardial fractional shortening determined in the absence of an adrenergic stimulus], in the presence of an isoproterenol challenge, noninfarct-zone LV systolic myocardial dysfunction manifested in a significant reduction in LV Ees in SHR-MI compared with WKY-MI and SHR and WKY-Sham rats ( P < 0.04). In conclusion, these data suggest that with chronic MI, the hypertensive heart is susceptible to the development of myocardial dysfunction, a change that cannot be attributed to excessive chamber dilatation, apoptosis, or necrosis, but which in turn contributes toward a reduced cardiac adrenergic inotropic reserve.

Effects of an aging vascular model on healthy and diseased hearts

The vitamin D(3) and nicotine (VDN) model is a model of isolated systolic hypertension (ISH) due to arterial calcification raising arterial stiffness and vascular impedance similar to an aged and stiffened arterial tree. We therefore analyzed the impact of this aging model on normal and diseased hearts with myocardial infarction (MI). Wistar rats were treated with VDN (n = 9), subjected to MI by coronary ligation (n = 10), or subjected to a combination of both MI and VDN treatment (VDN/MI, n = 14). A sham-treated group served as control (Ctrl, n = 10). Transthoracic echocardiography was performed every 2 wk, whereas invasive indexes were obtained at week 8 before death. Calcium, collagen, and protein contents were measured in the heart and the aorta. Systolic blood pressure, pulse pressure, thoracic aortic calcium, and end-systolic elastance as an index of myocardial contractility were highest in the aging model group compared with MI and Ctrl groups (P(VDN) < 0.05, 2-way ANOVA). Left ventricular wall stress and brain natriuretic peptide (P(VDNxMI) = not significant) were highest, while ejection fraction, stroke volume, and cardiac output were lowest in the combined group versus all other groups (P(VDNxMI) < 0.05). The combination of ISH due to this aging model and MI demonstrates significant alterations in cardiac function. This model mimics several clinical phenomena of cardiovascular aging and may thus serve to further study novel therapies.