For most people, the mental image of a heart attack is straightforward: a major artery becomes severely blocked, blood flow stops, and the heart suffers damage as a result. It is a useful picture, but an incomplete one. Cardiologists regularly encounter patients who have suffered a genuine heart attack despite angiograms showing no significant blockage at all, leaving both patients and families confused about what actually happened.
A heart attack without a blocked artery
This condition has a clinical name: MINOCA, or Myocardial Infarction with Non-Obstructive Coronary Arteries. It describes exactly what it sounds like: clear evidence of a heart attack on blood tests and heart tracings, yet no major blockage visible on angiography. Far from being rare or purely academic, MINOCA accounts for a meaningful proportion of heart attacks, particularly in younger patients and women.
Why this happens
Several mechanisms can explain a heart attack in the absence of an obvious blockage. A small plaque may rupture and cause a blood clot that partially dissolves before the angiogram is performed, leaving little visible trace. Coronary artery spasm, a sudden and temporary tightening of the artery wall, can cut off blood flow briefly but severely. Microvascular dysfunction, affecting the tiniest blood vessels within the heart muscle that angiograms cannot properly visualise, is another recognised cause. Less commonly, a spontaneous tear within the artery wall, known as spontaneous coronary artery dissection, can also trigger a heart attack without a classic blockage.
Clearing the myth
A dangerous misconception is that a clean or near-clean angiogram means the heart is entirely safe going forward. This is not necessarily true. Patients diagnosed with MINOCA still require careful evaluation and, in many cases, ongoing treatment and monitoring, because the underlying cause has simply been less visible rather than absent. Dismissing symptoms because "the arteries looked fine" can be a genuinely costly mistake.
Why this matters for diagnosis
Because standard angiograms are designed primarily to detect major blockages, additional tests are sometimes needed when a heart attack occurs without one. These may include specialised imaging of the heart muscle, tests assessing the smaller blood vessels, or further investigation into clotting tendencies. Reaching an accurate diagnosis matters, as the treatment approach for coronary spasm differs considerably from that for microvascular disease or a dissection.
Who should be aware of this
This condition deserves particular attention among younger patients, women, and anyone experiencing classic heart attack symptoms, such as chest pain, breathlessness, unusual fatigue or palpitations, even if initial tests suggest the arteries appear normal. Symptoms should never be dismissed purely on the basis of a single test result.
The key takeaway
A blocked artery is one path to a heart attack, but not the only one. Recognising that the heart can be genuinely injured without a visible blockage is essential for both patients and clinicians, ensuring symptoms are taken seriously and appropriate follow-up investigation is pursued, rather than reassurance being offered prematurely based on an incomplete picture.
The author is the Director – Cardiology at the CK Birla Hospital®, Delhi.
The opinions expressed in this article are those of the author and do not purport to reflect the opinions or views of THE WEEK.
