Opposite effects of the remodeling of infarcted and non-infarcted myocardium on left ventricular function early after infarction in humans. An echocardiographic study in patients examined before and after myocardial infarction

Heart Failure After ST-Elevation Myocardial Infarction: Beyond Left Ventricular Adverse Remodeling

ST-segment elevation myocardial infarction (STEMI) remains a significant source of morbidity and mortality worldwide. Despite advances in treatment leading to a significant reduction in the early complications and in-hospital mortality, a significant proportion of STEMI survivors develop heart failure (HF) at follow-up. The classic paradigm of HF after STEMI is one characterized by left ventricular adverse remodeling (LVAR) and encompasses the process of regional and global structural and functional changes that occur in the heart as a consequence of loss of viable myocardium, increased wall stress and neurohormonal activation, and results in HF with reduced ejection fraction (HFrEF). More recently, however, with further improvements in the treatment of STEMI the incidence and entity of LVAR appear to be largely reduced, yet the risk for HF following STEMI is not abolished and remains substantial, identifying a new paradigm by which patients with STEMI present with HF and preserved EF (HFpEF) characterized by reduction of diastolic or systolic reserve independent of LVAR.

Asynchrony of Left Ventricular Systolic Performance After the First Acute Myocardial Infarction in Patients with Narrow QRS Complexes: Doppler Tissue Imaging Study

BACKGROUND

Left ventricular (LV) electromechanical delay results in asynchronized contraction. However, it is not known if the presence of cardiac diseases without QRS prolongation may result in interventricular or intraventricular asynchrony. Doppler tissue imaging is now established for detecting regional contractile abnormalities and asynchrony in the LV.

OBJECTIVES

The aim of the study was to assess the degree of LV asynchrony after the first acute myocardial infarction (AMI) in patients with a narrow QRS complex using Doppler tissue imaging and correlate this with the site and extent of the infarction.

METHODS

Echocardiography with Doppler tissue imaging was performed within 1 week of AMI in 155 patients and compared with 50 age- and sex-matched healthy volunteers. Regional myocardial velocities were assessed at the 4 mitral annular sites, and the corresponding systolic velocity (Sm), early diastolic velocity (Em), time to peak Sm (Ts), and time to peak Em (Te) were measured. To assess LV synchronicity, SDs of Ts (Ts-SD) and Te (Te-SD) of all the 4 mitral annular sites were computed. Location and size of infarct were confirmed by echocardiographic wall-motion score index.

RESULTS

QRS complex duration was normal in all patients. Wall-motion score index was significantly higher in patients with anterior than inferior AMI (2.02 +/- 0.34 vs 1.24 +/- 0.21, P < .001). Ts-SD was significantly higher in patient than control group, and in patients with anterior than inferior AMI (38.21 +/- 2.59 vs 21.06 +/- 0.52 milliseconds and 43.18 +/- 3.77 vs 33.24 +/- 1.4 milliseconds, respectively, P < .001 for each), whereas Te-SD did not differ significantly among these groups (20.35 +/- 1.77 vs 18.17 +/- 1.14 milliseconds and 21.6 +/- 1.35 vs 19.1 +/- 1.11 milliseconds, respectively, P > .05 for each). A strong positive correlation was detected between LV systolic asynchrony (Ts-SD) and wall-motion score index (r = .77), LV mass (r = .67), LV end-systolic dimension (r = .65), and LV end-diastolic dimension (r = .5). The correlation was negative with LV ejection fraction (r = -.70) and Sm (r = -.6); the correlation was weak with Em (r = -.33) (P < .001 for all). In multivariate logistic regression analysis, infarct size was found to be the most independent predictor for systolic asynchrony (odds ratio 3.59, 95% confidence interval [1.43-9.33], P < .001).

CONCLUSION

AMI has a significant impact on regional myocardial contractility and LV systolic (but not diastolic) synchronicity early in the course even in the absence of QRS widening or bundle branch block. The degree of LV systolic asynchrony is greater with anterior than inferior AMI and mainly determined by infarct size.

Left ventricular systolic asynchrony after acute myocardial infarction in patients with narrow QRS complexes

BACKGROUND

The aim of the study was to assess the degree of left ventricular (LV) asynchrony after myocardial infarction (MI) in patients with a narrow QRS complex using tissue Doppler imaging (TDI) and correlate this with the site and extent of the infarction measured by contrast-enhanced magnetic resonance imaging (Ce-MRI).

METHODS

Echocardiography with TDI and Ce-MRI was performed within 6 days of acute MI in 47 patients and compared with 69 age-matched healthy volunteers. Regional myocardial velocities were assessed in 12 segments, and the corresponding systolic velocity (Sm), early diastolic velocity (Em), as well as the time to peak Sm (Ts) and time to peak Em (Te) were measured. To assess LV synchronicity, SDs of Ts (Ts-SD) and Te (Te-SD) of all 12 segments were computed. Location and size of infarct were confirmed by Ce-MRI with a 16-segment model.

RESULTS

All the patients had a normal QRS complex duration. The Ts-SD was significantly prolonged in the MI group when compared with controls (42.2 +/- 13.7 vs 18.0 +/- 7.0 milliseconds, P < .001). The Ts-SD was longer in patients with anterior than inferior MI (46.8 +/- 13.9 vs 34.6 +/- 8.5 milliseconds, P = .002). Stepwise multiple regression analysis revealed that infarct size was the main independent predictor of systolic asynchrony ( B = 0.79, 95% CI 0.75-1.23, P < .001). Asynchrony was not related to the transmurality of the infarction.

CONCLUSIONS

Myocardial infarction has a significant impact on LV synchronicity even in those with a narrow QRS complex. The degree of LV systolic asynchrony is mainly determined by the infarct size and not transmurality.

Myocardial viability independently influences left ventricular diastolic function in the early phase after acute myocardial infarction

BACKGROUND

After acute myocardial infarction, a broad range of left ventricular (LV) end-diastolic pressure (LVEDP) is expected because of chamber remodeling. However, intrinsic characteristics of the infarcted tissue (necrosis or viability) may also play a role. We aimed to evaluate whether myocardial viability (Mviab) has an influence on LVEDP.

METHODS

One hundred twenty-three consecutive patients with acute myocardial infarction underwent low-dose dobutamine echocardiography (5-10 microg/kg/min) to assess Mviab. Mviab was quantitatively evaluated by the variation of Delta wall motion score index. Patients underwent left heart catheterization with recording of LVEDP and a complete echocardiographic examination with measurement of LV volumes, ejection fraction, and mass.

RESULTS

The overall population (81% male; mean age 58 +/- 10 years) was divided into 2 groups according to the presence (group 1; 66 patients) or absence (group 2; 57 patients) of Mviab. LVEDP was higher in patients without Mviab (16 +/- 8 vs 20 +/- 7 mm Hg; P =.02). The multivariate analysis showed that Delta wall motion score index correlated with LVEDP (P =.01) independent of wall motion score index and LV end-systolic volume.

CONCLUSIONS

After acute myocardial infarction, LVEDP shows wide variability and is independently associated with Mviab.

Biphasic survival response to amlodipine after myocardial infarction in rats: Association with cardiac vascular remodeling

In clinical studies, calcium channel blockers have been found to cause adverse cardiovascular reactions after myocardial infarction; however, such effects appear limited to short-acting agents. Thus, our aim was to evaluate the response to a long-acting calcium channel blocker, amlodipine, in terms of both survival and, cardiac and vascular remodeling after infarction. One week after permanent coronary occlusion, rats were randomized to no treatment or daily amlodipine (5 mg/kg) continued for up to 9 months. Amlodipine resulted in improved survival at 200 days (65% versus 26%; p < 0.05), but no difference at 9 months. However, rats with large infarcts died earlier than untreated animals, while those with smaller infarcts died later or survived for nine months. Amlodipine produced no difference in collagen content in non-infarcted tissue or myocyte cross-sectional area versus untreated hearts; however, scar length was increased. In addition, amlodipine was associated with vascular remodeling; muscle:lumen ratio increased in non-infarcted myocardium as did perivascular fibrosis. Vessels within the scar had reduced lumen area because of smooth muscle proliferation. We also examined infarcted hearts subjected to one week of intravenous amlodipine (1 mg/kg) initiated before occlusion and examined three weeks later. In this study, amlodipine exacerbated muscle proliferation in infarct vessels and was associated with less scar collagen. The vascular remodeling associated with amlodipine treatment is considered unfavorable and so the adverse survival for rats with large infarcts was no surprise. However, the prolonged survival associated with smaller infarcts raises the possibility that these vascular changes, under certain circumstances, are beneficial.