Intracoronary trimetazidine does not improve recovery of regional function in a porcine model of repeated ischemia

Animal models of myocardial infarction: Mainstay in clinical translation

Preclinical models with high prognostic power are a prerequisite for translational research. The closer the similarity of a model to myocardial infarction (MI), the higher is the prognostic value for clinical trials. An ideal MI model should present cardinal signs and pathology that resemble the human disease. The increasing understanding of MI stratification and etiology, however, complicates the choice of animal model for preclinical studies. An ultimate animal model, relevant to address all MI related pathophysiology is yet to be developed. However, many of the existing MI models comprising small and large animals are useful in answering specific questions. An appropriate MI model should be selected after considering both the context of the research question and the model properties. This review addresses the strengths, and limitations of current MI models for translational research.

Trimetazidine protective effect against ischemia-induced susceptibility to ventricular fibrillation in pigs

PURPOSE

Ventricular fibrillation (VF) is a possible consequence of brief myocardial ischemia. Such a short ischemia does not provoke cell damage, but induces changes in intracellular cardiac metabolism due to diminished oxygen supply to the heart. Trimetazidine (TMZ) is a drug able to restore the metabolic balance between fatty acid and glucose oxidation in ischemic myocardial cells. The aim of this double-blind study was to investigate TMZ effect on VF in pigs during short-term ischemia.

METHODS

Ischemia was induced after thoracotomy by complete, but brief (1 min) occlusion of the left anterior descending coronary artery under electrical stimulation. The ventricular fibrillation threshold (VFT), heart rate (HR), various hemodynamic parameters and malondialdehyde (MDA) blood levels were measured before and during ischemia in two groups of eight anesthetized pigs. The mass of ischemic myocardial tissue was also evaluated.

RESULTS

No effects on either the HR or the hemodynamic parameters were observed during myocardial ischemia, whereas TMZ increased the VFT and decreased both MDA blood levels (an index of lipid peroxidation) and the ischemic area.

CONCLUSIONS

TMZ limited ischemia-induced electrical dysfunction leading to cardiac susceptibility to VF by decreasing lipid peroxidation and maintaining ionic homeostasis. TMZ could therefore provide protection against ischemia-induced VF.

Protective effects of trimetazidine on hypoxic cardiac myocytes from the rat

The electrophysiological effects of the antianginal drug trimetazidine (TMZ) were investigated in cultured rat ventricular myocytes using a substrate-free hypoxia model of ischemia. The transmembrane potentials were recorded with glass microelectrodes and the contractions were simultaneously monitored with a video motion detector. The cardiomyocytes were treated with TMZ (1-5.10(-4) M final concentration) in the bath. The untreated and the drug-treated cells were submitted either to 150 min normoxia or to 150 min hypoxia followed by 90 min reoxygenation in the absence of oxidizable substrate. In normoxic conditions, TMZ did not affect the maximal diastolic potential (MDP) but significantly lowered the plateau potential level (OS) and decreased the upstroke velocity (Vmax) and the spontaneous action potential rate (APR). Conversely, TMZ significantly increased action potential duration at 80% repolarization (APD80). Under substrate-free hypoxia, the untreated cells displayed a progressive contractile failure and an important decrease in OS and APD. In parallel, early postdepolarizations triggering high rate spikes were observed. Prolonging oxygen depletion led to the cessation of the spontaneous electrical activity and thereafter to a gradual decrease in MDP. Near normal rhythmic action potentials and contractions resumed after reoxygenation. Comparatively, the treatment by 5.10(-4) M TMZ almost completely prevented the decrease in plateau amplitude, resting membrane potential, Vmax, APD80, and rate caused by substrate-free hypoxia. Moreover, the hypoxia-induced arrhythmias and the cessation of spontaneous electromechanical activities did not occur in the presence of TMZ (5.10(-4) M). After reoxygenation, the TMZ-treated cells exhibited a higher action potential amplitude than that of the untreated cells, although the TMZ-induced depressive effects on the spontaneous frequency and the Vmax persisted. In conclusion, this study shows that TMZ (5.10(-4) M) is efficient in protecting the isolated cardiac myocytes against the functional alterations induced by substrate-free hypoxia and led thus to a better recovery upon reoxygenation. The cytoprotective action may be linked, at least in part, to apparent ion channel blocking effects of the drug, which appeared in basal conditions at concentrations used in this study.

Effect of trimetazidine on postischemic regional myocardial stunning in the halothane-anesthetized dog

Trimetazidine (TMZ) has been described as a new antiischemic agent. Whereas its precise mechanism of action remains unknown, antioxidant properties and the ability to preserve high-energy phosphate metabolism have been reported. Accordingly, we studied whether TMZ may limit postischemic regional myocardial stunning (known to be caused by reactive oxygen species) and influence recruitment of contractile reserve by inotropic stimulation in a dog model, using halothane to maintain steady anesthesia throughout the experiment. Dogs were submitted to a 15-min coronary artery occlusion followed by reperfusion. The blinded protocol included a 3-day oral pretreatment (1 mg/kg/day), a bolus injection (0.5 mg/kg), followed by intravenous infusion (0.5 mg/h) initiated 15 min before coronary artery occlusion. Despite lower heart rate (HR) and significant reduction of lipid peroxidation in treated dogs, myocardial stunning and recruitment of contractile reserve by dobutamine infusion in the postischemic myocardium were not modified by TMZ. Adenine nucleotide pool in the postischemic myocardium was considerably reduced as compared with the nonischemic myocardium in both groups. Therefore, in halothane-anesthetized dogs, the antioxidant properties of TMZ were not sufficient to protect myocardium in terms of postischemic dysfunction after 15-min ischemia.

Myocardial protection during coronary artery bypass graft surgery: a randomized, double-blind, placebo-controlled study with trimetazidine

We conducted a randomized, double-blind, placebo-controlled study to assess the cardioprotective effects of trimetazidine (TMZ), an antiischemic drug, on left ventricular function using transesophageal echocardiography (TEE) after coronary artery bypass grafting (CABG). Forty patients undergoing elective CABG received either TMZ or a placebo (PCB). The primary measures of efficacy were serial measurements of fractional area change (FAC), percent of systolic wall thickening (SWT), and malonedialdehyde (MDA) production. The two groups were similar for the following variables: number of vessels revascularized (2.5 +/- 0.2 in the TMZ group and 2.8 +/- 0.1 in the PCB group), duration of aortic clamping (46 +/- 4 min in the TMZ group and 48 +/- 3 min in the PCB group), and bypass time (63 +/- 4 min in the TMZ group and 70 +/- 4 min in the PCB group). FAC increased by 12% in both groups 20 min after aortic unclamping (P < 0.05) and remained above the initial value at the sixth postoperative hour. SWT was 23.8% +/- 1.6%, 25.4% +/- 1.9%, then 21.6% +/- 1.5% in the TMZ group and 22.8% +/- 1.6%, 23.8% +/- 1.4%, then 22.3% +/- 1.6 % in the PCB group, after induction of anesthesia and 1 and 6 h after aortic unclamping (not significant). MDA increased by 24% in the PCB group and 25% in the TMZ group 20 min after aortic unclamping (P < 0.01). Lactate levels were lower in the TMZ group (P < 0.05) and patients from the TMZ group received less intravenous calcium before aortic clamping (P < 0.02) and less calcium channel entry blocking drugs in the early phase after aortic unclamping (P < 0.01) compared to the PCB group. We conclude that in patients with good preoperative ejection fraction undergoing CABG, TMZ as administered did not demonstrate clinically significant cardioprotective effects on left ventricular performance and lipid peroxidation compared to PCB.