The term 'heart attack' is used to describe a sudden blockage of a coronary artery by a blood clot, which results in the blood supply to part of the heart muscle (myocardium) being cut off. The person affected will classically experience crushing chest discomfort. The result of such a blockage is progressive and irreversible damage (infarction) to the heart muscle and possible sudden death due to heart rhythm disturbance. The outcome for those who survive is largely determined by the extent and severity of the residual damage after treatment.
For over 20 years various thrombolytic (clot busters) drugs given intravenously have been used to try and reopen blocked coronary arteries and restore coronary flow (reperfusion), with proven success in the majority of patients in whom they are used. However, approximately 30 per cent of patients may not be eligible for such treatment (because of various contraindications) and in about 20 to 30 per cent of those who are given thrombolysis the coronary artery renarrows or occludes some hours or days later, sometimes causing further infarction. 

Ambulance paramedics

Thrombolysis has usually been given in hospital, but in the West it is increasingly being administered by ambulance paramedics on first clinical contact with the patient, often at their home. This has the advantage of treatment being given to the patient at an earlier stage in the development of their heart attack.

Primary angioplasty uses a more mechanical approach. The coronary artery is reopened using a small balloon catheter with, more recently, the addition of a stent (a cylindrical metal meshwork tube) which is inserted into the artery to hold it open. Of those patients having reperfusion treatment for heart attack, increasing number of patients who would have previously been treated with thrombolytic drugs are now receiving primary angioplasty. Primary angioplasty is contraindicated in very few patients, and there is a low risk of subsequent blockage or renarrowing of the coronary artery and a lower risk of stroke. There is wide consensus that it provides superior outcomes compared with thrombolysis provided that it can be delivered quickly.

Extensive research has shown that the outlook for patients having a heart attack is closely related to the length of time the coronary artery remains blocked; the longer the duration of the blockage the higher the mortality and morbidity that results.

Timely delivery

Patients may live some distance from a hospital with facilities for primary angioplasty, making it difficult to achieve the 'timely' delivery required to achieve optimum outcomes. There is currently a widely held view that primary angioplasty may lose some of its advantage over thrombolysis if the additional delay incurred in waiting for primary angioplasty is 60 to 90 minutes more than the time when thrombolysis could have been given. Thus, the advantage of primary angioplasty over thrombolysis in relation to saving lives may depend on the difference between the time it takes to deliver thrombolysis and the time it takes to start the angioplasty. It is suggested that primary angioplasty will be most effective (and hence more cost-effective) if delivered within this 60 to 90 minutes timeframe.

Primary angioplasty

The time intervals outlined above are those currently recommended in international guidelines for the management of heart attack patients. However, there is continuing debate over whether longer delays in delivering primary angioplasty may still achieve better results than thrombolysis, particularly for patients presenting more than three hours after the onset of their heart attack. Intuitively this is plausible because with increasing time, the blood clot blocking a coronary artery becomes more firm and less amenable to dissolution by thrombolytic drugs. Further clinical trials may help to clarify this issue and may increase the number of patients eligible for primary angioplasty who currently live too far from a service, or where transport is difficult.

 The issue of acceptable time delay is therefore one that continues to be debated and may change in future.  The bottom-line is when one has the symptoms suggestive of a heart attack, he or she should go to the nearest tertiary care hospital with cardiac cathlab facility and 24 x 7 availability of trained interventional cardiologists who can perform a quick angioplasty.

The authors are consultant cardiologists,
Columbia Asia Hospitals.