Preoperative electrocardiogram (ECG) are routinely ordered in adults undergoing noncardiac
surgery, yet ECG abnormalities have not been found to predict postoperative cardiac
complications. Abnormal ECG findings may lead to unnecessary preoperative medical
consultation and cardiac imaging. Preoperative NT-proBNP has been shown to enhance
cardiac risk prediction and has not been compared to ECG.
METHODS AND RESULTS
We included a consecutive sample of 1000 patients seen at the preoperative assessment
clinic prior to elective noncardiac surgery at a single tertiary-care centre. Eligible
patients were either 65 years or older, or 45 to 64 years with at least one risk factor
according to the Revised Cardiac Risk Index (RCRI). Mean age was 67.3 years (standard
deviation 9.5), 53.7% were male, 52.6% had hypertension, 23.7% diabetes, and 13.6%
prior history of coronary artery disease. Two thirds (63.1%) underwent surgery with
overnight stay, the remainder had same-day surgery. The majority (97.1%) of patients
had a preoperative ECG ordered, of which 51.2% had at least one abnormal ECG finding.
The most common abnormal ECG findings as reported by the automated ECG interpretation
were supraventricular arrythmias (181/971; 18.6%), non-specific ST-T waves abnormalities
(99/971; 10.2%) and previous myocardial infarction (134/971; 13.8%). Following the
abnormal ECG findings, 8.0% (95% confidence interval [CI] 6.0%-10.8%) of patients
had a preoperative medical consultation or cardiac imaging ordered. Routine preoperative
NT-proBNP was obtained in 29.3% (293/1000), of which 34.8% (102/293) had NT-proBNP
≥200 ng/L. For patients who underwent inpatient surgery (n=631), the 30-day incidence
of major cardiac complications was 5.9% (95% CI 4.3%-8.0%). No ECG finding was associated
with postoperative cardiac events, alone or in combination. A preoperative ECG finding
of partial or complete left bundle branch block and supraventricular arrythmia had
a weak correlation with preoperative NT-proBNP ≥200 ng/L (Pearson's R 0.185 p=0.003
and 0.202 p=0.001, respectively). In patients who had a preoperative NT-proBNP measured
and underwent in-hospital surgery, NT-proBNP ≥200 ng/L was independently associated
with postoperative major cardiac events (adjusted odds ratio 6.68, 95% CI 2.22-19.56).
In patients undergoing elective noncardiac surgery, abnormal findings were common
on routine ECG and led to medical consultation or cardiac imaging in 1 in 12 patients.
Abnormal ECG findings were not associated with postoperative cardiac events but preoperative
NT-proBNP was a strong predictor of cardiac complications. Clinicians may consider
using NT-proBNP for preoperative cardiac risk stratification in patients with abnormal
ECG findings to identify patients at higher risk.