50-year-old felt chest pain for 20 minutes. Then it vanished: What test revealed a silent heart attack?

An angiogram revealed the real problem: a 95 per cent blockage in the circumflex artery, one of the vessels that supplies blood to the heart and is located in the back of the chest cavity. He underwent immediate angioplasty (a procedure to open up the artery). A stent (a mesh bridge to keep the artery walls wide) was implanted. My patient had suffered a heart attack which hides in plain sight.

A different kind of heart attack

This was a Non-ST-Elevation Myocardial Infarction, or NSTEMI. This does not elevate the ST-segment of your ECG, a visual marker of a heart attack and damage, and therefore, tends to get overlooked if the patient is not tested for troponin. In regular or STEMI heart attacks, the ST-segment of the ECG is consistently elevated.

This silent heart attack is caused by a partial or temporary blockage of a coronary artery, restricting blood flow to the heart muscle rather than completely stopping it. Even though the blockage is partial, it is significant enough to cause damage to the heart tissue, just as an easily detectable heart attack. Also, since the circumflex artery is located in the back and ECG electrodes are placed only on the front of the torso and limbs, changes here are not picked up that easily. In other words, the heart attack may simply be occurring in a place the ECG does not easily see. In reality, NSTEMI is as common as STEMI, and in many cases can be more dangerous if it goes unrecognised. That’s why a troponin test is the best way to ascertain any kind of heart attack.

The unstable clot

In a classic heart attack, a blood clot abruptly seals off the artery, cutting off blood supply completely. In NSTEMI, the clot behaves differently. It is usually a platelet-rich clot — often referred to as a “white thrombus.” Rather than causing a fixed obstruction, it may form, partially dissolve and reform, creating intermittent blockage. This unstable pattern explains why patients often report chest pain that comes and goes. The pain may last 10 or 20 minutes, disappear and then recur hours later. Because the symptoms settle temporarily, many people delay seeking medical attention.

Yet this instability is most risky. The clot can suddenly expand and convert into a full blockage, triggering a massive heart attack.

Why treatment is different

In classic heart attack cases, doctors often use clot-dissolving drugs known as thrombolytics if immediate angioplasty is not available. But these drugs do not work well in NSTEMI because the clot is platelet-rich rather than being fibrin-rich, fibrin being a tough, insoluble fibrous protein essential for blood clotting. Instead, treatment focuses on antiplatelet medications and blood thinners to stabilise the clot, along with statins to control cholesterol and stabilise arterial plaques.

An angiogram is usually performed soon after diagnosis to identify the blocked arteries. Many patients undergo angioplasty with stent placement, though in roughly one-third of cases bypass surgery may be required, particularly if multiple arteries are severely narrowed.

Interestingly, cardiologists often find that NSTEMI patients have more widespread coronary artery disease than those with the regular kind.

The warning that should never be ignored

The patient who arrived with a short episode of chest pain was fortunate. His symptoms were investigated promptly, the blockage was identified and the artery was opened before extensive damage occurred. But his case carries a broader lesson. Sometimes the most dangerous heart attack is not the one that announces itself loudly.

My patient recovered well. But he will now remain on statins, blood thinners and strict lifestyle modification for life.

(Dr Shetty is lead cardiologist, Sparsh Hospital, Bengaluru)