Myocardial ischaemia during endoscopic procedures

‘Cardiac ischaemia and rhythm disturbances during elective colonoscopy’ by George et al in Frontline Gastroenterology 2010;1:131–7 merits comment. The number of colonoscopies continues to rise with the introduction of the bowel cancer screening programme. Apart from the potential complications of bleeding, perforation and oversedation, the cardiovascular effects of colonoscopy have not been studied in great detail. Two controlled studies examining the cardiovascular effects of colonoscopy have reported bradycardia, hypotension and ventricular ectopics.^{1 2} George et al's study is the first prospective, double-blind trial that provides objective evidence of potential clinically significant ischaemic (ST-T wave) changes and rhythm disturbances during elective colonoscopy in patients with known heart disease and to a lesser extent in those patients with a known cardiovascular risk profile. The study also confirms that there is no increased cardiovascular risk in healthy fit individuals who undergo colonoscopy.³

There will be a doubling of the population aged between 65 and 80 years old by 2030.⁴ Increasing age is an independent risk factor for coronary artery disease in asymptomatic individuals. Autopsy studies have shown a prevalence of obstructive coronary artery disease varying between 10% and 20% in the fourth decade and 50–70% in the eight decade.⁵ Consequently, we will perform more endoscopic procedures on an ageing population with a potential for significant cardiac injury.

Myocardial ischaemia is known to occur during upper gastrointestinal endoscopy including endoscopic retrograde cholangiopancreatography (ERCP).^6–9 Tachycardia alone is an important factor in the development of myocardial ischaemia during endoscopy.^{6 9} In 1996, Rosenberg et al conducted a prospective double-blind randomised controlled trial to assess the efficacy of metoprolol compared with placebo in preventing myocardial ischaemia during ERCP.¹⁰ This study showed that all patients (n=38) had a tachycardia during ERCP, but the rate in the metoprolol group was significantly lower compared with placebo. Eleven (29%) patients developed myocardial ischaemia (ST changes) during their ERCP, all related to tachycardia. Only one such event developed in the metoprolol arm (n=19). This is the only trial demonstrating the use of β-blockers in preventing myocardial ischaemia in patients undergoing endoscopic procedures. However, in this study, patients did not receive preoxygenation with supplemental oxygen, received morphine rather than pethidine and larger doses of hyoscine bromide were used than is common in Britain. Several other studies^11–13 have demonstrated that the use of β-blockers prior to certain forms of non-cardiac surgery reduces cardiac complications (ischaemia and arrhythmia) and were incorporated in the American College of Cardiology and American Heart Association guidelines in the past.¹⁴

Like colonoscopy, ERCP can be a very challenging procedure and a significant proportion of ERCPs are carried out in the elderly population. Lessons from previous studies and the study by George et al can be extrapolated to ERCP practice. There may be a role for β-blockers in preventing cardiac ischaemia in high-risk patients during endoscopic procedures (ERCP and colonoscopy). This needs further investigation in view of the recent perioperative ischaemic evaluation trial,¹⁵ which demonstrated that β-blockers were not associated with any significant reduction in the risk of all-cause mortality, cardiovascular mortality or heart failure, but were associated with a reduction in non-fatal myocardial infarction (number needed to treat (NNT)=63) and myocardial ischaemia (NNT=16) at the expense of an increase in non-fatal strokes (number needed to harm (NNH)=293). In terms of safety outcomes, β-blockers were associated with a high risk of perioperative bradycardia requiring treatment (NNH=22) and perioperative hypotension requiring treatment (NNH=17) without any increased risk of bronchospasm.

Following the results of the trial conducted by Rosenberg et al in 1996, we have been using metoprolol prior to ERCP at the University North Tees to reduce the risk of cardiac ischaemia and arrhythmias for the past 10 years without any complications (including strokes) after carefully screening patients for contraindications to β-blockers.