Semi-Minimal Invasive Method to Induce Myocardial Infarction in Rats and the Assessment of Cardiac Function by an Isolated Working Heart System.

Myocardial infarction (MI) remains the main contributor to morbidity and mortality worldwide. Therefore, research on this topic is mandatory. An easily and highly reproducible MI induction procedure is required to obtain further insight and better understanding of the underlying pathological changes. This procedure can also be used to evaluate the effects or potency of new and promising treatments (as drugs or interventions) in acute MI, subsequent remodeling and heart failure (HF). After intubation and pre-operative preparation of the animal, an anesthetic protocol with isoflurane was performed, and the surgical procedure was conducted quickly. Using a minimally invasive approach, the left anterior descending artery (LAD) was located and occluded by a ligature. The occlusion can be performed acutely for subsequent reperfusion (ischemia/reperfusion injury). Alternatively, the vessel can be ligated permanently to investigate the development of chronic MI, remodeling or HF. Despite common pitfalls, the drop-out rates are minimal. Various treatments such as remote ischemic conditioning can be examined for their cardioprotective potential pre-, peri- and post-operatively. The post-operative recovery was quick as the anesthesia was precisely controlled and the duration of the operation was short. Post-operative analgesia was administered for three days. The minimally invasive procedure reduces the risk of infection and inflammation. Furthermore, it facilitates rapid recovery. The "working heart" measurements were performed ex vivo and enabled precise control of preload, afterload and flow. This procedure requires specific equipment and training for adequate performance. This manuscript provides a detailed step-by-step introduction for conducting these measurements.

In vivo and ex vivo functional characterization of left ventricular remodelling after myocardial infarction in mice.

AIMS: The interest in cardiac remodelling (REM) has steadily increased during recent years. The aim of this study was to functionally characterize REM following myocardial infarction (MI) in mice using high-end in vivo and ex vivo methods. METHODS AND RESULTS: Myocardial infarction or sham operation was induced in A/J mice. Six weeks later, mice underwent cardiac magnetic resonance imaging and were subsequently sacrificed for ex vivo measurements on the isolated heart. Thereafter, hearts were trichrome stained for infarction size calculation. Magnetic resonance imaging showed significantly reduced ejection fraction (P < 0.01) as well as increased end-systolic and end-diastolic volumes (P < 0.01) after MI. The mean infarct size was 48.8 ± 6.9% of left ventricle. In the isolated working heart coronary flow (time point 20': 6.6 ± 0.9 vs. 13.9 ± 1.6 mL/min, P < 0.01), cardiac output (time point 20': 17.5 ± 2.6 vs. 36.1 ± 4.3 mL/min, P < 0.01) and pump function (80 mmHg: 2.15 ± 0.88 vs. 4.83 ± 0.76, P < 0.05) were significantly attenuated in MI hearts during all measurements. Systolic and diastolic wall stress were significantly elevated in MI animals. CONCLUSION: This two-step approach is reasonable, since data quality increases while animals are not exposed to major additional interventions. Both the working heart and magnetic resonance imaging offer a reliable characterization of the functional changes that go along with the development of post-MI REM. By combining these two techniques, additional information such as wall stress can be evaluated.