When to perform pre-operative ECG

Clinical evaluation prior to surgery in many countries is left to anesthesiologists. However, cardiologists are frequently involved in preoperative evaluation as well, because cardiac complications have the highest clinical and prognostic relevance for most interventions. Cardiovascular complications occur for example in 1-5% of all vascular surgical procedures (1). A classic and virtually mandatory component of preoperative evaluation is the 12-lead electrocardiogram (ECG).

The aim of this brief review is to present the current role, indications, and interpretation of preoperative ECG and the subsequent management of patients depending on its results.

1 - Risk stratification prior to operation

The purpose of preoperative clinical evaluation is to detect the clinical circumstances which can lead to worsened outcomes.

A) For patients undergoing cardiac surgery, there are more than 20 published risk scores, which include dozens of demographic and clinical variables; the most commonly used are the EuroSCORE, the Cleveland Clinic and the CABDEAL models (2).

B) For noncardiac surgery, both in cardiac and noncardiac patients, many risk models have been used as well; no single index has shown clear superiority for predicting cardiac complications (3). Current risk stratification guidelines are based on the presence or absence of a number of factors classified into three groups in descending order of risk: active cardiac conditions, intermediate risk predictors and minor risk predictors (4).

2 - Preoperative electrocardiogram

Rest ECG is considered an inherent part of routine preoperative evaluation in many clinical practice guidelines, but American guidelines include abnormal ECG in the minor risk predictors category, that is, not independently associated with an increased perioperative risk (4). This statement applies only to cardiac patients though, as will be developed below. In noncardiac patients, guidelines also state that an abnormal ECG should prompt a cardiologist consultation (4).

It has been shown that the mere classification of ECGs into normal or abnormal improves the prognostic capabilities of clinical evaluation alone in noncardiac patients (5), as assessed taking into account both patient (see before) (4) and surgery (Table 1) risks. For preoperative purposes, an "abnormal" ECG is defined as (see Table 2): left ventricular hypertrophy; pathological q waves or ST-segment shift; and some abnormal rhythms (atrial fibrillation/flutter, pacemaker rhythm, ventricular ectopics) (5). Rest sinus tachycardia (of course not related to the disease requiring surgery) should probably be added to this list, as some studies have shown a close relationship with cardiac events (6).

Nevertheless, more than half of preoperative ECGs are abnormal and rarely does this finding lead to modifying the therapeutic approach or correlates with outcomes in low-risk patients (7). On the other hand, the prognostic information obtained from the preoperative ECG is relevant in coronary patients (8).

Apart from socio-economic reasons, some authors have questioned that routine ECG would add prognostic value to a thorough clinical examination in patients undergoing noncardiac operations - as cardiac surgery, on its own, requires a complete cardiovascular evaluation, which obviously includes an ECG. (9).

3 - The proposed algorithm

Figure 1 shows the proposed algorithm for the evaluation of all patients undergoing noncardiac surgery (4,9). Without entering into the debate about which specialists should be in charge of the initial evaluation of surgical candidates, the algorithm considers that ECGs should be ordered for patients:
(i) undergoing emergency operations;
(ii) at high risk due to comorbidities (heart failure, coronary disease, cerebrovascular disease, diabetes, renal insufficiency, uncontrolled hypertension); and
(iii) for high or intermediate-risk procedures (low-risk being those performed under local or locoregional anaesthesia, dental procedures, endoscopic surgery, and breast, endocrinologic, gynecologic, and plastic and reconstructive surgery).
Finally, a thorough cardiological evaluation (history and physical examination, ecocardiogram and possibly a stress test for ischemia) if rest ECG is abnormal.




Table 1: Cardiac risk of noncardiac surgical procedures (modified from ref. 4)

Table 2 : Criteria for abnormal preoperative ECG (in noncardiac patients) (modified from ref. 5)

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology