Routine use of antegrade cardioplegia underestimates the risk of regional myocardial ischemia especially in right coronary disease

Aims: Regional myocardial acidosis, measured with newly developed tissue-pH electrodes, represents regional myocardial ischemia and assesses inadequate myocardial protection. It is known that pH-levels are independently associated with patients long-term survival.

Methods: 52 pts underwent intramyocardial tissue-pH guided CABG. We prospectively monitored pH (corrected to 37°XC) from the anterior and posterior left ventricular wall, in patients (gr. A, n=19) with highly stenotic RCA (≥95%) versus those (gr. B, n=33) without occlusive disease to the RCA (<50%). pH-values led to individual cardioplegia application. Optimal metabolic protection was defined as pH of >6.85, which has been shown to be predictive of favorable postoperative outcome. Need for inotropics, pre-/postoperative CI and troponin-levels were measured.

Results: Integrated pH-levels during aortic-clossclamping (mean time gr. A 56±21min versus gr. B 51±23min) for gr. B were 7.23±0.13 in the anterior wall respectively 7.25±0.12 in the posterior wall. pH-value of the posterior wall was with 6.84±0.11, significantly lower (p=0.039) in gr. A, while anterior wall showed pH-value of 7.25±0.14. Myocardial temperature revealed similar results with 19.4±1.9°C for gr. A versus 19.1±2.3°C for gr. B in the anterior wall. Posterior wall temperature was significantly (p=0.046) higher in gr. A versus gr. B (21.9±3.0°C vs. 18.4±2.1°C).ll but two pat. (89%) in gr. A versus 61% in gr. B required inotropic support early postoperatively (p=0.041).

Conclusions: This is the first study to show that regional myocardial acidosis of the posterior wall, a preventable condition, occurs frequently and underestimated in stenotic RCA with impact on clinical outcome. We recommend, to respond individually on metabolic changes by an adopted cardioplegia application.