RISK CALCULATION
So what does cardiac risk mean to a cardiologist evaluating patients for surgery? Frequently the surgical component of the risk is unknown to the cardiologist since they do not participate in surgeries and are unaware of the surgical stresses placed on the patient via differing surgical procedures. There are charts of relative surgical stressors on the body used by some cardiologists and in some risk calculators, but cardiologists do not have the in depth knowledge about the surgeon’s skills or complication rate of individual surgeons in considering these charts. So risks in the view of the cardiologist most often are based solely on the chance of a perioperative myocardial infarction and cardiac related death. While these outcome measures are important, they do not necessarily reflect the intraoperative risk of severe blood pressure changes, clinically significant dysrhythmias, heart failure (right or left), or ischemia.
The most common risk tools for cardiologists are the revised cardiac risk index (RCRI) also called the Lee index, the NSQIP (American College of Surgeons National Surgical Quality Improvement Program) online calculator, and the myocardial infarction or cardiac arrest calculator (MICA). The RCRI is the oldest and most validated of these calculators and therefore the most often used. Older models such as the Goldman cardiac risk index, Detsky modified risk index, and the Eagle criteria have largely been abandoned due to better models being available. These models (RCRI, NSQIP, MICA) provide a percent risk of MI or death. Cardiologists use these percentages to define further testing. For low risk patients (<1%) no further testing is performed. Patients with higher risk are subjected to additional testing at some point before or after surgery, not to alter the outcome of surgery (or management of anesthesia) but to lower long term risk. Herein lies the dichotomy that leads higher risk patients to warrant testing, but the testing may not be done until after the surgery. This creates a vacuum of information for the anesthesiologist who may find the testing to be very valuable before surgery to answer questions about risks due to diastolic or systolic heart failure, valvular disease impact, ischemia, and dysrhythmia management intraoperatively.
One element of the risk indexes include surgery-specific risks (RCRI, NSQIP) with the risk of MI or death being stratified at more than 5% (high risk procedures), 1-5% (intermediate risk procedures), and <1% (low risk procedures). Emergency surgery is associated with a significant increase in risk with cardiac complications being 2-5 times higher than for elective procedures. Other risk measures include history of ischemic heart disease, heart failure, cerebrovascular disease, and insulin dependent diabetes (all RCRI). Preop serum creatinine elevation >2 for RCRI and >1.5 for NSQIP is also a risk factor. Increasing age, ASA class, and preoperative functional status are part of the NSQIP risk stratification. Atrial fibrillation is a greater risk factor than a diagnosis of coronary artery disease. Obesity increases risks for adverse cardiovascular events at the time of non cardiac surgery but is not a predictor of end-organ damage.
The RCRI was first published in 1999 and is used worldwide. It is predictive of major cardiac complications (cardiac death, MI, cardiac arrest, postoperative cardiogenic pulmonary edema and complete heart block) in all types of elective major surgeries with the exception of abdominal aortic aneurysm surgery, lower extremity bypass surgery, and endovascular surgery. Because some cardiologists (or their midlevels) do not know the limitations of the RCRI, they calculate the risk inappropriately using the RCRI in these surgeries. A vascular surgery cardiac risk calculator (VSGNE) has been developed for vascular procedures and should be used instead. The RCRI also underestimates the risk of complete heart block or heart failure, issues that are important intraoperatively to the anesthesiologist. The RCRI is located at
Revised Cardiac Risk Index for Pre-Operative Risk - MDCalc
The Gupta (MICA) risk calculator is located online at
Gupta Perioperative Cardiac Risk | Calculate by QxMD . This calculator uses 5 variables that are input online: type of surgery, dependent functional status, abnormal creatinine, ASA class, and increased age. It is an easy to use calculator that outperforms the RCRI for MI or cardiac arrest, either intraoperatively or postoperatively.
The NSQIP is more cumbersome to use requiring input of 20 patient factors plus the surgical procedure. It has excellent correlation to mortality, morbidity, and 6 other outcome factors. It is located at
ACS Risk Calculator - Home Page
