Evidence-based guidelines recommend that after a heart attack, the blocked coronary artery needs to be reopened quickly by either fibrinolysis (or “clot-busting” drugs) or primary percutaneous coronary intervention (primary PCI), which aims to open the artery using balloons and stents. However, there are several reasons for delay in these treatments.

Firstly, “patient delay” is the delay from the onset of chest pain or symptoms to when a call is made to emergency medical services, and can only really be reduced by better public education about heart attacks. Secondly, “system delay” is a combination of “transportation delay” (the time taken for the patient to get to the hospital) and “door-to-balloon delay” (the time taken for the patient to receive the artery-opening therapy once they are in the hospital). In terms of training of doctors and measurement of outcomes within hospitals and across health systems, there has been a huge focus on the “door-to-balloon” delay. However, to know the effect of delaying therapy on outcome, we need to look at “system delay”, which is what a Danish study does in this week’s JAMA.

Due to excellent public medical databases in Denmark, the authors were able to study over 6000 patients with the particular form of heart attack (“STEMI”) which is best treated by primary PCI, and obtain estimates for the various types of delay outlined above. The authors excluded patients with a treatment delay greater than 12 hours or a system delay greater than 6 hours.

Interestingly, treatment delay and patient delay were not associated with mortality, but the authors are quick to assert that “should not deter encouraging patients to seek medical help as soon as possible after the onset of symptoms”. On the other hand, system delay predicted mortality, with a hazard ratio of 1.10 per 1-hour delay. In other words, for every one hour of system delay, there is a 10% increase in mortality. When the authors analysed further, they found that a 1-hour transportation delay led to 10% increase in mortality, whereas a 1-hour door-to-balloon delay led to a 14% increase in mortality. In other words, time does really mean muscle (and life) when it comes to the heart.

Most medical students will recognize the quote:

‘Half of what you'll learn in medical school will be shown to be either dead wrong or out of date within five years of your graduation; the trouble is that nobody can tell you which half—so the most important thing to learn is how to learn on your own.’

Dave Sackett: “Old fart from the frozen north” “Father of EBM”

The rapid assessment and treatment of a patient with a heart attack is drummed into most medical students very early on in their training. ABC: airway, breathing, circulation. Part of that resuscitation is the delivery of Oxygen to patients with a heart attack, mainly due to the fact the flow of oxygenated blood in the heart is stopped for a period of time.

The idea for providing oxygen in a heart attack is it may improve the amount of oxygen of the cells in the heart that are dying mainly due to the lack of oxygen, ultimately reducing pain and the size of the dead heart muscle. To most this will make sense in terms of pathophysiological reasoning.

Today a Cochrane review by Cabello and Burls on Oxygen therapy for acute myocardial infarction looks at the evidence from randomised controlled trials to establish whether routine use of inhaled oxygen in acute heart attack infarction improves patient-centred outcomes, in particular pain and death.

Now, here is the half of what is learnt learn that may eventually be out of date:

Three trials involving 387 patients were included and 14 deaths occurred. The pooled relative risk of death was 2.88 (95% confidence interval 0.88 to 9.39) in an intention-to-treat analysis and 3.03 (95% confidence interval 0.93 to 9.83) in patients with confirmed heart attack.

While suggestive of harm, the small number of deaths recorded meant that this could be a chance occurrence. Basically, there is no conclusive evidence from randomised controlled trials to support the routine use of inhaled oxygen in patients with acute heart attack.

The neat thing about EBM is you are never really sure of which half is out of date; this review adds to that half. As the reviewers rightly state, we need an urgent large scale trial to unpick the uncertainty.

Coronary heart disease (CHD), which usually presents as a heart attack (or myocardial infarction, MI) is the most common cause of death and disability both in the UK and globally. The way in which CHD is treated and prevented therefore has huge implications for patients, health professionals and policymakers. Once a person has a heart attack, prevention of further heart attacks, stroke or death, or secondary prevention, is crucial. There is strong evidence for benefit of several drugs and treatments after heart attacks to this end, including aspirin, statins, ACE inhibitors and beta-blockers. Such treatments have undoubtedly saved lives, but studies in the US and the UK, have shown that between 30-60% of MI patients receive appropriate treatment. There are strong arguments for giving more people the right drugs with benefits in terms of mortality and cost-effectiveness. Current NICE guidelines therefore recommend these treatments for all patients following a heart attack.

This week, the British Heart Foundation reported that only 38% of such patients were receiving adequate rehabilitation care. “Cardiac rehab includes advice from dieticians, physiotherapists and psychologists about how to live with the consequences and improve the survival chances following heart attacks, coronary artery bypass operations and angioplasties.” The components of cardiac rehab have benefits individually and together. For example, a review of 46 trials including 9000 patients showed that exercise-based rehabilitation reduces all deaths by 20%, and cardiac deaths by 26%. Some patients are too ill to benefit from cardiac rehabilitation, and others choose not to partake or continue with the rehabilitation programme.

Provision of drug treatment and primary angioplasty programmes has improved more than cardiac rehabilitation, which has remained the poor relation. This is partly because we tend to favour treatment rather than prevention, and pills rather than behaviour changes. To a greater extent than other treatments, cardiac rehabilitation needs the commitment of the patient. However, this does not mean that we cannot be innovative in designing ways of increasing access to this vital aspect of care for patients after MI.