Role of intravenous beta-blockers in the treatment of ST-elevation myocardial infarction: of mice (dogs, pigs) and men

Physiological insights of recent clinical diagnostic and therapeutic technologies for cardiovascular diseases

Diagnostic and therapeutic methods for cardiovascular diseases continue to be developed in the 21st century. Clinicians should consider the physiological characteristics of the cardiovascular system to ensure successful diagnosis and treatment. In this review, we focus on the roles of cardiovascular physiology in recent diagnostic and therapeutic technologies for cardiovascular diseases. In the first section, we discuss how to evaluate and utilize left ventricular arterial coupling in the clinical settings. In the second section, we review unique characteristics of pulmonary circulation in the diagnosis and treatment of pulmonary hypertension. In the third section, we discuss physiological and anatomical factors associated with graft patency after coronary artery bypass grafting. In the last section, we discuss the usefulness of mechanical ventricular unloading after acute myocardial infarction. Clinical development of diagnostic methods and therapies for cardiovascular diseases should be based on physiological insights of the cardiovascular system.

Intracoronary followed by intravenous administration of the short-acting β-blocker landiolol prevents myocardial injury in the face of elective percutaneous coronary intervention

BACKGROUND

Myocardial injury during elective percutaneous coronary intervention (PCI) is associated with higher subsequent cardiac events and mortality. β-Blockers have been used to reduce myocardial injury during ischemia and reperfusion. We investigated whether intracoronary followed by intravenous administration of the short-acting β-blocker landiolol prevents myocardial injury in the face of elective PCI.

METHODS AND RESULTS

Patients undergoing elective PCI (n=70) were randomly assigned to the landiolol (n=35) or control (n=35) group. Landiolol or saline was administered into target vessels through a balloon catheter for 1min before and after first balloon inflation followed by continuous intravenous administration for 6h after PCI. The incidence of myocardial injury defined by cardiac troponin-I (cTnI) >/=0.05 ng/ml was 79% of the patients in the control group compared to 56% in the landiolol group (p=0.04). The cTnI level at 24h after PCI tended to be lower in the landiolol group (0.57 ± 1.14 versus 1.27 ± 2.48 ng/ml; p=0.07), while the CK-MB level was not significantly different between the landiolol and control groups. The incidence of peri-procedural myocardial infarction defined by cTnI >/=0.12 ng/ml was significantly (p=0.02) lower in the landiolol group (41%) compared to the control group (70%). There was no incidence of coronary spasm, hypotension, bradycardia or heart failure during and after PCI in the two groups.

CONCLUSIONS

Brief intracoronary followed by continuous intravenous administration of landiolol is safe and effective for myocardial protection in the face of elective PCI.

The cardioprotection granted by metoprolol is restricted to its administration prior to coronary reperfusion

BACKGROUND

Myocardial infarct size is a strong predictor of cardiovascular events. Intravenous metoprolol before coronary reperfusion has been shown to reduce infarct size; however, it is unknown whether oral metoprolol initiated early after reperfusion, as clinical guidelines recommend, is similarly cardioprotective. We compared the extent of myocardial salvage associated with intravenous pre-reperfusion-metoprolol administration in comparison with oral post-reperfusion-metoprolol or placebo. We also studied the effect on suspected markers of reperfusion injury.

METHODS

Thirty Yorkshire-pigs underwent a reperfused myocardial infarction, being randomized to pre-reperfusion-metoprolol, post-reperfusion-metoprolol or placebo. Cardiac magnetic resonance imaging was performed in eighteen pigs at day 3 for the quantification of salvaged myocardium. The amounts of at-risk and infarcted myocardium were quantified using T2-weighted and post-contrast delayed enhancement imaging, respectively. Twelve animals were sacrificed after 24h for reperfusion injury analysis.

RESULTS

The pre-reperfusion-metoprolol group had significantly larger salvaged myocardium than the post-reperfusion-metoprolol or the placebo groups (31 ± 4%, 13 ± 6%, and 7 ± 3% of myocardium at-risk respectively). Post-mortem analyses suggest lesser myocardial reperfusion injury in the pre-reperfusion-metoprolol in comparison with the other 2 groups (lower neutrophil infiltration, decreased myocardial apoptosis, and higher activation of the salvage-kinase phospho-Akt). Salvaged myocardium and reperfusion injury pair wise comparisons proved there were significant differences between the pre-reperfusion-metoprolol and the other 2 groups, but not among the latter two.

CONCLUSIONS

The intravenous administration of metoprolol before coronary reperfusion results in larger myocardial salvage than its oral administration initiated early after reperfusion. If confirmed in the clinical setting, the timing and route of β-blocker initiation could be revisited.