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CALCIUM ANTAGONISTS REDUCE MYOCARDIAL INFARCTION AFTER CARDIAC SURGERY

Department of Anesthesia, Toronto General Hospital, University Health Network, Toronto, Ontario, M5G 2C4

INTRODUCTION

Calcium channel blockers (CCBs) may reduce cardiac complications following cardiac surgery. Observational studies however question their effectiveness^1,2. We therefore carried out a meta-analysis of all randomized controlled trials (RCTs) evaluating CCBs in cardiac surgery.

METHODS

Eligible studies were RCTs comparing CCBs to non-CCBs during coronary-artery-bypass-grafting or valve surgery, and reporting one of the following perioperative outcomes: mortality, myocardial infarction (MI), myocardial ischemia or atrial fibrillation/supraventricular tachyarrthymias (SVT). Patients enrolled after developing SVTs were excluded. Studies were retrieved from MEDLINE and EMBASE with no language restriction: (Calcium channel blockers) and (Postoperative complications or Perioperative care or Intraoperative complications). Titles and abstracts were evaluated to exclude ineligible studies. The remaining studies were then read to determine eligibility. Bibliographies were surveyed to identify eligible studies. Study quality was rated using the scale of Jadad et al, a 5-point scale assessing blinding, randomization and withdrawal documentation. The minimal score required was 1/5. Quality assessment and data abstraction were performed by both authors; disagreements were resolved by consensus. Treatment effects were estimated using odds ratios (OR) and the random effects model (Review Manager 4.1). In the calculation of summary estimates of treatment effects, this model places more emphasis on larger studies with more subjects and outcomes. Subsequently, subgroup analyses were performed for CCB class (diltiazem, verapamil, dihydropyridines) and non-CCB class (nitrates, nitroprusside).

RESULTS

Our search yielded 1813 studies. Thirty-seven studies, encompassing 3105 patients, qualified for analysis. The Breslow-Day test for heterogeneity was negative for the primary analysis. CCBs significantly reduced perioperative ischemia (OR 0.48, 95% CI 0.33-0.68) and MIs (OR 0.58, 95% CI 0.37-0.91), but had no effect on mortality (OR 1.01). In subgroup analyses, CCBs were superior to nitrates in reducing ischemia (OR 0.65, 95% CI 0.40-1.05) and MIs (OR 0.44, 95% CI 0.21-0.93). In addition, postoperative atrial fibrillation and SVTs were significantly reduced among patients receiving non-dihydropyridine CCBs.

DISCUSSION

This systematic review of the perioperative use of CCB's shows significantly reduced myocardial ischemia and infarction after cardiac surgery. In subgroup analyses, CCB's were superior to nitrates. An adequately powered RCT is therefore justified.

REFERENCES

1 Anesthesiology 69:343-7.

2 Anesthesiology 68:676-80.

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