The classic heart attack symptom of pain radiating to the left chest and arm has been put into question by a study based on cardiac troponin assays.

In a review of which symptoms were predictive of acute MI defined by high sensitivity cardiac troponin T (CTnT) levels, Australian and international researchers found that radiation to the right arm or shoulder was a stronger predictor of acute MI and also linked to larger myocardial infarct size.

The TRAPID-AMI (High Sensitivity Cardiac Troponin T assay for rapid Rule-out of Acute Myocardial Infarction) study found there were only four symptoms that were independently predictive of the diagnosis of acute MI: radiation to the right arm or shoulder (Odds Ratio 3.0); chest pressure (OR 2.5), chest pain worsened by physical activity (OR 1.7) and pain radiation to the left arm or shoulder (OR 1.7).

The study was conducted in 1282 people presenting with chest pain in 12 centres, of whom 213 (18%) were diagnosed with acute MI on the basis of a significant rise and fall pattern in cardiac troponin T levels and ECG changes.

In the entire cohort, 10% of patients had right arm or shoulder radiation, 35% had left arm or shoulder radiation, 70% had chest pressure and 30% had pain worsened by physical activity.

While there were four symptoms that independently predicted acute MI, no single one was particularly predictive (around 13%), though a diagnosis of acute MI was much more likely in patients with more than one of these key symptoms (55% diagnosis in patients with all four).

However, the duration of symptoms was not predictive of acute MI and there were no symptoms that were predictive of non-MI.

When troponin levels were divided into four quartiles representing variation in infarct size, those patients with larger acute MI were more likely to have ‘pulling’ chest pain, pain the right upper chest and right arm/shoulder radiation. In contrast, patients with smaller acute MI as judged by troponin levels were more likely to have radiation of pain to the back (ventral radiation), although these symptoms occurred in only a few patients (up to 6.6%).

The study authors said their findings suggested that the classic symptoms of acute MI – and its severity, may need to be re-thought in the troponin era.

However they cautioned that their study did not include patients without chest pain,  (up to one third of patients with acute MI) and had few patients with atypical non-cardiac symptoms.