Etiology of Myocardial Injury Following Non-cardiac Surgery - a Prospective Clinical Trial

Introduction:

It is estimated that > 200 million patients in the world undergo surgery each year of which approximately 10 million would suffer from a myocardial injury in the perioperative period. Mortality is high in this group of patients since it often goes undiagnosed, the patho-physiology of myocardial injury is unclear, non-invasive diagnostic tools are not widely available and treatment is unknown.

Multiple studies have shown that > 10% of patients > 65 years and undergoing non-cardiac surgery have an increase in Troponin T (TnT). In the POISE study including 8331 patients, the authors found that 5.7% of the placebo group suffered from a myocardial injury within the 30-day postoperative period. In the recently published data from the VISION study including > 15,000 patients, the authors demonstrated that patients with peak perioperative TnT values of < 0.01, 0.02, 0.03-0.29 and > 0.30 ng/L had a 30-day mortality of 1%, 4%, 9.3% and 16.9% respectively. Furthermore, an elevated TnT without symptoms or ECG changes are an independent predictor of 30-day mortality. It is possible that some cases of myocardial injury in Non-cardiac surgery (MINS) result from oxygen supply-delivery mismatch due to severe perioperative hypotension, and possibly persistent tachycardia but coronary artery thrombosis cannot be excluded in these patients. It is well known that surgical trauma causes an increase in several pro-inflammatory cytokines which, together with sympathetic over-activity, leads to a hypercoagulable state due to platelet activation, and a predisposition to thrombosis. In one study, it was found that approximately 1/3 of the patients had evidence of intracoronary thrombosis at autopsy.

Myocardial infarction with non-obstructive coronary artery (MINCA) has recently received greater attention in the literature. The underlying patho-physiology responsible for MINCA revealed the presence of a typical myocardial infarct on cardiac magnetic resonance imaging in only 24% of patients, with myocarditis occurring in 33% and no significant abnormality in 26%. A rare cause of MINCA is Takotsubo cardiomyopathy, also called stress cardiomyopathy. Recently, coronary angiography using computerized tomographic angiography (CTA) has added a new dimension to the diagnostic armamentarium available to the clinician. Using advanced imaging techniques and low radiation, it is today possible to determine quite accurately coronary artery anatomy and thereby determine stenotic lesions in the coronary vasculature. Echocardiography can be easily performed by an experienced technician, the images stored digitally and evaluated subsequently by specialists. The availability of continuous perioperative monitoring of several hemodynamic indices as well as regular blood gas analysis, may enable determination of oxygen demand-supply mismatch.

Methods: