Summary

Improving door-to-balloon time (time from the onset of symptoms to reperfusion of the affected coronary artery) is, at present, the best way to improve survival after a heart attack. The target time is 90 minutes or less.

Introduction

It's obvious that cutting off the blood supply to a muscle will result in its eventual death, so it's not too surprising that restoring the blood supply to ischemic (i.e. limited blood supply) heart muscle is a life-saving procedure. For patients with an ST-segment elevation myocardial infarction, called a STEMI, rapid treatment with angioplasty can be lifesaving, but time is of the essence. Studies have shown that faster 'door-to-balloon times' (the time from arrival at the hospital to the deployment of the balloon or artery-opening device) produce clinically meaningful differences in survival. If there's a significant delay in angioplasty, it may be better to start fibrinolytic therapy (intravenous streptokinase or other drugs to dissolve the clot). To be effective, fibrinolytic therapy must be started within 2 to 3 hours after the onset of symptoms; it has little benefit if given after 12 hours.

The first 3 hours

The 3-hour time window available for successful fibrinolytic treatment is also valid for primary percutaneous coronary intervention (PCI), i.e the symptom-to-balloon time must (or certainly should be) be less than 3 hours. But how much benefit can be achieved when this time is shortened further? And can this be quantified? A review in the New England Journal of Medicine attempts to answer these questions.

Data from the US National Registry of Myocardial Infarction show a strong association between door-to-balloon time and death in hospital, based on almost 30,000 patients with STEMIs. For each 15-minute decrease in door-to-balloon time from 150 minutes to less than 90 minutes, there were about 6 fewer deaths per 1000 patients treated. In addition to fewer deaths, faster times are likely to benefit quality of life in survivors because of improved 'rescue' of jeopardized heart muscle.

While guidelines state that the door-to-balloon time should be less than 90 minutes, hospital performance studies show that more than half of STEMI patients experience longer waits. In particular, patients who are transferred from one hospital to another for emergency PCI seldom have total door-to-balloon times of less than 90 minutes.

This means that, given these problems, one should establish a time-point after which administration of fibrinolytic therapy would be a better approach than PCI. Available data suggest that if it takes more than 90 - 120 minutes longer to provide PCI than fibrinolytic therapy, then fibrinolytic therapy is preferred. An exception might be if there is shock, as such patients may derive greater benefit from PCI.

How to shorten the critical time

How can hospitals improve their door-to-balloon times? There are several simple and inexpensive strategies include that can be achieved by cutting through traditional hierarchies and red-tape:

• Pre-hospital ECG, with possible bypass of emergency department and direct access to the cath lab
• allow emergency medicine physicians to activate the cath lab
• have the activation require only a single phone call
• expect the cath lab team be ready within 20 to 30 minutes of the call
• clear cath lab of elective cases
• implement a system for rapid data feedback about cases in progress.

Currently, a US national initiative is promoting the adoption of these strategies, with the goal of having 75% of PCIs done within in 90 minutes or less. More than 900 U.S. hospitals are participating, and an evaluation will be made in 6 months. Anecdotal reports suggest that improvement is occurring in many hospitals throughout the country. The challenge now is for every hospital to achieve this goal.

A combined approach?

There will always be occasional delays that will impact achieving the target of 90 minutes or less. Not surprisingly, attempts have been made to minimize the impact of such delays by combining the two reperfusion strategies - PCI and fibrinolytic therapy. In one strategy, called 'facilitated PCI', reperfusion with a fibrinolytic and a glycoprotein IIb/IIIa receptor blocker (Tirofiban, which counteracts platelet aggregation) is used followed by emergency PCI as soon as possible. Clinical trials have not shown this to be a more beneficial approach than PCI alone - indeed it may be harmful. But this poor result may because the studies were done at hospitals where emergency PCI was already speedy.

Another strategy is the 'pharmacoinvasive' approach, in which emergency PCI is not done after fibrinolytic therapy as a routine, but is reserved for those cases with failed reperfusion; this is also called 'rescue PCI'. With this method, non-emergency PCI is then done the next day.

Conclusions

The efforts being made to shorten door-to-balloon times will certainly bear fruit. They represent the translation of information about best practices into everyday practice, transforming what was once extraordinary performance into routine care. As always, such efforts rely on the cooperation of all the people concerned, with team-based approaches achieving the best results.