Key result
Sham cardio-thoracic surgery in rats caused a significant early increase in left ventricular mass normalized to body weight (2.19 vs. 1.85 mg/g, p<0.05) at 1 week.
Absolute Event Rate: 2.19% vs 1.85%
p-value: p=<0.05
Cardio-thoracic surgical procedures in experimental myocardial infarction models cause distinct alterations in global organism integrity and long-term circumscribed repercussions on cardiac morphology and function, which must be considered when interpreting basic cardiovascular research.
Sham surgery elevates early LV mass in rat controls; supports caution when interpreting sham arms in experimental MI studies.
BACKGROUND: Surgical procedures in small animal models of heart disease might evoke alterations in cardiac morphology and function. The aim of this study was to reveal and quantify such potential artificial early or long term effects in vivo, which might account for a significant bias in basic cardiovascular research, and, therefore, could potentially question the meaning of respective studies. METHODS: Female Wistar rats (n = 6 per group) were matched for weight and assorted for sham left coronary artery ligation or control. Cardiac morphology and function was then investigated in vivo by cine magnetic resonance imaging at 7 Tesla 1 and 8 weeks after the surgical procedure. The time course of metabolic and inflammatory blood parameters was determined in addition. RESULTS: Compared to healthy controls, rats after sham surgery showed a lower body weight both 1 week (267.5±10.6 vs. 317.0±11.3 g, n<0.05) and 8 weeks (317.0±21.1 vs. 358.7±22.4 g, n<0.05) after the intervention. Left and right ventricular morphology and function were not different in absolute measures in both groups 1 week after surgery. However, there was a confined difference in several cardiac parameters normalized to the body weight (bw), such as myocardial mass (2.19±0.30/0.83±0.13 vs. 1.85±0.22/0.70±0.07 mg left/right per g bw, p<0.05), or enddiastolic ventricular volume (1.31±0.36/1.21±0.31 vs. 1.14±0.20/1.07±0.17 µl left/right per g bw, p<0.05). Vice versa, after 8 weeks, cardiac masses, volumes, and output showed a trend for lower values in sham operated rats compared to controls in absolute measures (782.2±57.2/260.2±33.2 vs. 805.9±84.8/310.4±48.5 mg, p<0.05 for left/right ventricular mass), but not normalized to body weight. Matching these findings, blood testing revealed only minor inflammatory but prolonged metabolic changes after surgery not related to cardiac disease. CONCLUSION: Cardio-thoracic surgical procedures in experimental myocardial infarction cause distinct alterations upon the global integrity of the organism, which in the long term also induce circumscribed repercussions on cardiac morphology and function. This impact has to be considered when analyzing data from respective animal studies and transferring these findings to conditions in patients.
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Nordbeck et al. (2013) studied Healthy rats (sham model for heart disease) (n=12). Sham thoracic surgery (thoracotomy and pericardiotomy) vs. Untreated control was evaluated on Left ventricular myocardial mass normalized to body weight at 1 week (mg/g) (p=<0.05). Sham cardio-thoracic surgery in rats caused a significant early increase in left ventricular mass normalized to body weight (2.19 vs. 1.85 mg/g, p<0.05) at 1 week.
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