Background: Hypertension (HT) increases cardiac afterload and is one of the risk factors of poor prognosis after myocardial infarction (MI). However, there is little information on how HT impacts the healing processes during sub-acute phase MI. We investigated the role of an increased afterload on left ventricular (LV) performance and remodeling shortly after MI.
Methods: Anterior MIs were created in 15 Yorkshire pigs via percutaneous access. To mimic HT condition, 7 pigs (Banding, n=7) underwent surgical banding of the ascending aorta 10 days after the MI, and were compared to the remaining pigs (Control, n=8). LV remodeling and function were assessed one month after MI using 3-D echocardiography and invasive hemodynamic measurements.
Results: Echocardiographic assessment at day 10 revealed no significant differences in LV ejection fraction (EF) or LV volumes. One month after MI, aortic banding increased the systemic vascular resistance index, but was not statistically significant (1658±282 dyn/s/cm5/m2 vs 1153±658 dyn/s/cm5/m2, P=0.08). Banding group presented with significantly impaired LVEF (Figure, P=0.002), larger end systolic volume (Figure, P=0.045), lower cardiac index (3.1±0.9 L/min/m2 vs 4.4±0.6 L/min/m2, P=0.01), and elevated LV end diastolic pressure (22.4±5.0 mmHg vs 14.4±7.5 mmHg: P=0.04, Banding vs Control, respectively). Reduced EF was associated with remote myocardial dysfunction and histological analysis revealed increased interstitial fibrosis in this area.
Conclusion: Increased afterload in sub-acute phase of MI induces more severely impaired cardiac function and LV remodeling, and was associated with worse heart failure status.