Cirugia no cardiaca, hipotension y necrosis miocardica

More than one in five patients at high cardiovascular risk show signs of heart muscle necrosis immediately after undergoing non-cardiac elective surgery, Australian research has found.
Seventy nine patients out of 352 undergoing elective surgery at a Sydney hospital showed elevation in a high-sensitivity troponin T assay (hs-TnT) in the 48 hours after their operation.
Only seven patients (2%) showed clinical evidence of MI, so without the very sensitive hs-TnT assay, the myocardial necrosis in the others would not have been detected, said the authors, led by Professor David Brieger of Concord Repatriation General Hospital.
Myocardial necrosis was more likely to occur in older patients; if there had been a period of hypotension during the operation; and if the operation was an orthopaedic procedure, the authors found.
Intraoperative hypotension (defined as systolic blood pressure of 100mg Hg or less) occurred in 70% of patients, lasting for about half an hour on average. Increasing the period of hypotension “strongly predicted myocardial necrosis.”
The findings suggested “The most common mechanism [for the myocardial necrosis] is likely to be a mismatch between myocardial oxygen supply and demand rather than thrombus formation on vulnerable plaque”, the authors said.
The authors measured hs-TNT in all the patients before the surgery and found that 31% had raised levels (greater than 14ng/litre). Having elevated levels before the operation did not increase the likelihood of myocardial damage during the operation.
The authors commented that a high incidence of perioperative cardiac events after orthopaedic surgery had been reported in other studies. They speculated that subclinical fat embolism could be an underlying cause.
All of the patients were on antiplatelet therapy and 80% were taken off this before the operation. The authors commented that this went against current guidelines, although no link was found between anti-platelet therapy cessation and perioperative myocardial necrosis in their cohort.
Heart 2012: doi:10.1136/heartjnl-2011-301577