CHICAGO – Remote ischemic preconditioning reduced the risk of myocardial injury following angioplasty in patients with peripheral artery occlusive disease, and appeared to improve clinical outcome in an ongoing prospective study of 64 patients.
The rise in cardiac troponin I blood levels was significantly attenuated 24-hours after angioplasty (with or without stenting) in patients who were randomized to remote ischemic preconditioning applied 1 hour before surgery at the arm via three cycles of 5-minute blood pressure cuff inflation, followed by 5 minutes of deflation, compared with those receiving no preconditioning (log 0.025 mcg/L vs. 0.240 mcg/L; P = .01).
Preprocedure troponin levels among the 64 consecutive patients were similar between arms (log 0.042 mcg/L vs. 0.046 mcg/L; P = .94).
At 1-year follow-up, two patients in the control group experienced an acute MI, compared with none in the preconditioned group, Dr. Jeanne Adele Lubbe said at the annual meeting of the World Federation of Vascular Societies. Acute MI was defined according to American Heart Association guidelines, and took into account cardiac troponin levels, electrocardiographic changes, and clinical symptoms.
"This is clinically significant, and suggests that the magnitude of cardiac troponin I release has prognostic value," she said.
Audience members described the findings as surprising and intriguing, as several studies have reported an effect on troponin levels with remote ischemic preconditioning but were unable to tie this to a clinical effect – much less in a group of patients who were considered at relatively low risk for a cardiac event.
Comparisons were also made between preconditioning and the protective effects observed with perioperative beta blockade in some surgical patients. "If this pans out further down the track ... is this the sort of thing you’d chase?" one attendee asked.
Dr. Lubbe replied, "To think that blowing up a blood pressure cuff would have a lasting effect is a bit strange. But this is not something that we’re going to start applying to patients without having a firming up of this effect."
Preconditioning can be applied to patients with claudication and is ideal in patients who are known to be at high risk of MI, especially if it can be predicted when they are at the highest risk for myocardial ischemia, explained Dr. Lubbe of the University of Stellenbosch in Tygerberg, South Africa.
Among the 32 control and 32 study patients, there were no differences in the number of stents placed during angioplasty (eight vs. nine), stent length (mean, 118 mm vs. 143 mm), balloon inflation pressure (mean, 9.5 atmospheres vs. 10.1 atmospheres), or total fluoroscopic screening time (mean, 25 minutes vs. 20.5 minutes).
At baseline, there were no significant differences between the control and experimental groups in their use of beta blockers (66% vs. 44%), calcium channel blockers (13% vs. 25%), ACE inhibitors (50% vs. 72%), nitrate (13% vs. 3%), or nicorandil/glibenclamide (25% vs. 22%), Dr. Lubbe said.
Heart failure was present in 16% of patients in both arms, and 34% had a history of angina. Controls and patients undergoing preconditioning had similar rates of previous MI (22% vs. 16%) and coronary revascularization (13% vs. 6%). Dr. Lubbe noted that all patients could possibly be protected by the effect of antecedent chronic ischemia, but she said that this was minimized by instructing patients to avoid overexertion prior to the intervention.
The first control patient who was diagnosed with MI had undergone percutaneous transluminal arterial angioplasty (PTA) and stenting of a right-sided iliac artery stenosis prior to diagnosis of the MI, which was treated medically. The second patient experienced acute cardiac arrest 9 hours after undergoing PTA of his superficial femoral artery and posterior tibial vessels. Coronary angiogram revealed critical four-vessel disease, but the patient refused revascularization and subsequently died.
Dr. Lubbe and her colleagues are continuing to evaluate additional patients, and they plan to report 1- and 3-year major adverse cardiovascular and cerebrovascular events at a future meeting.
Dr. Lubbe and her coauthors report no conflicts of interest.