Dr Uday B Khanolkar/ Dr Biju Ephrem

The treatment of heart attack has evolved over the decades, mirroring the rapid advances in the speciality of cardiology at large.

The palliative care of the 1960s and 70s has been transformed by scientific evidence in to highly effective disease modifying treatments. Re-establishing  blood flow as quickly as possible remains the most importantprinciple underlying treatment of Heart Attack and Thrombolysis or Emergency (Primary) Angioplasty are the two principal methods.

Thrombolytics

Thrombolytics are clot-busting drugs and have been the mainstay of heart attack treatment for more than 3 decades. Last decade saw many newer thrombolytic drugs being introduced.  These are usually given by intravenous drip or boluses and activate an enzyme which breaks down blood clots restoring blood flow.  However it dissolves the clot in only 60-70 per cent of cases, with most of the benefit occcuring, if given with in 2 hrs of onset of heart attack; longer delay results in even lesser efficacy.This is because with increasing time, the blood clot becomes more firm and less amenable to dissolution.35 per 1000 lives are saved when it is used within the first hour of symptoms. This drops to 16 lives saved per thousand if treatment is delayed for 7 to 12 hours. 

The remaining 30-40 per cent of cases either die due to failed thrombolysis [failure of drug to lyse the clot], or even if they survive the attack, go home with a very weak heart due to a large portion of the heart muscle being permanently damaged. These patients who do survive with weak hearts go on to live with either heart failure, valve leaks, ruptures in the portion of the heart or rhythm problems [electrical disturbances] and have a very morbid and unproductive life.

Approximately  30 % of  patients may  not  be   eligible  for  thrombolytic treatment( because of various contraindications ) and in 20-30% of those who are given thrombolytics,  the artery renarrows or occludes within 4 weeks, sometimes resulting in another heart attack.Also more than half the patients treated with thrombolytic therapy continue to have a significant blockage (since the treatment breaks up blood clots but does nothing for the underlying stenosis) and reduced blood flow in the affected artery.

Primary Angioplasty

Coronary angioplasty is a technique for unblocking arteries carrying blood to the heart muscle. Primary angioplasty is  used to describe an angioplasty done as the main or first treatment for patients suffering a heart attack. The introduction of Primary Angioplasty by Meyer in 1982 was a revolutionary advance in the treatment of heart attack.

Procedure is performed under local anaesthesia by initially passing a guide wire across the block via an artery in the groin under X-ray guidance. This is followed by suctioning of the clot manually with the help of a catheter and syringe. This process of directly removing the clot under vision by Suction catheter helps in reestablishing blood flow immediately. Now to address the underlying block, a small balloon expandable stent at the tip of a catheter tube is inserted and guided to the blocked artery. It is then inflated which clears the fatty deposit blocking the artery and removed, leaving in place the 'stent' - acylindrical metal meshwork tube - to hold artery open. The whole procedure takes approximately half an hour.

Patients are simultaneously started on medicines, which helps in thinning the blood by preventingplatelets (one of the component of blood) from clumping together and forming a clot at the site of atherosclerotic plaque. Routinely prescribed drugs like aspirin is effective against only one of the pathways leading to platelet clumping. As a result, newer antiplatelet agents(GP11b/111a inhibitors)have been developed which block the final common pathway of platelet aggregation.Thesedrugs are delivered intravenously over a period of one to two days.

Who benefits the most ?

Those who have major attack or who are in Cardiogenic shock (extremely low BP) benefits the most with Primary angioplasty and this is the only treatment which seems to reduce their otherwise extremely high death rate as per the American Heart Association (AHA) Guidelines.  Patients who are at high risk of intracranial bleeding (especially elderly) and those with previous Bypass operation are also ideal candidates for Primary angioplasty.

Which is superior; Primary Angioplasty or Thrombolysis?

Where as thrombolytics succeed in only 60-70% of cases to restore blood flow, Primary angioplasty does this in >95% of the cases. With primary angioplasty, death rate during the heart attack is 60% lower compared to that with thrombolytic therapy. Thrombolytics may be limited by recurrence of heart attack and bleeding complications (like stroke). Primary angioplasty circumvents these limitations. The risk of repeat heart attack and stroke are reduced by almost 50 percent. Risk of heart failure is also reduced by 25 percent as pumping function is better preserved. The probability of having an open artery at 6 months with thrombolytic therapy is 60% versus 95% with primary angioplasty.

In addition, the hospital stay is shortened due to early recovery. As the rate of repeat heart attack after Primary Angioplasty is extremely low after 2nd  hospital day, selected low risk patients could be safely discharged after three days. On an average patients who have undergone Primary Angioplasty stay in hospital, around four to six days compared with seven to nine days after thrombolysis. Though initially costly, long-term expenses of primary angioplasty are much less than those of other treatment options. This is due to the fact that patients treated with primary angioplasty are less likely to have recurrence of symptoms and are much less likely to come back for hospitalizations. Hence according to AHA, Primary Angioplasty is superior in the short term as well as long term.

Rescue Angioplasty

Rescue  angioplasty is  used to describe an angioplasty done as the main  treatment for patients suffering a heart attack who fails to respond to thrombolytic therapy. In patients in whom thrombolytic therapy fails, AHA recommends immediate transfer to a hospital having facility for angiography and angioplasty.

Routine Early Angioplasty after Thrombolytic Therapy

Even patients who initially respond to thrombolytic therapy are also recommended by AHA to undergo coronary angiography and angioplasty as early as possible, preferably with in 24-48 hrs.  This helps in identifying those with residual block, prevent repeat attack and also helps in quicker recovery of the damaged heart.

Despite the advent of newer generation thrombolytics, angioplasty remains the gold standard for the treatment of heart attack. In the current era of newer generationstents, suction catheters and GP IIb/llla platelet inhibitors, the advantages of Angioplasty over thrombolytic therapy is even more dramatic.