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Treatment Delay Compromised STEMI Survival in Northern Ireland

MANCHESTER — The survival of patients experiencing an ST-segment elevation myocardial infarction (STEMI) in Northern Ireland may be being significantly affected by not being treated quickly enough, it was reported at the British Cardiovascular Society Annual Conference.

In a retrospective study, considering all STEMIs that had occurred in the country between January 2013 and March 2018, delayed revascularisation resulted in a 38% reduction in survival when compared to performing percutaneous coronary intervention (PCI) within guideline-recommend times.

European guidelines recommend that patients with STEMI need to be revascularised within 120 minutes of their diagnosis, with the preferred method being PCI, Dr Jack Laffan, one of the study's investigators, told Medscape News UK.

"In Northern Ireland, they don't use thrombolysis", said Dr Laffan. That means that if a patient lives in a rural area, they rely on being transported to a primary PCI centre for treatment, which are usually located in cities. 

"In the Republic of Ireland, we still use thrombolysis and we're actually trying to get more people to use it," added Dr Laffan, who works as a consultant cardiologist for the Belfast Health and Social Care Trust and Cork University Hospitals Group. 

"We know that the faster the arteries open, regardless of the method used to open them up, the better the outcome; you're trying to restore blood flow to the heart muscle and the longer the arteries are blocked, the more damage is done."

Data from the Northern Irish STEMI database were used for the analysis. Of the 3250 patients that were included, 2590 had received PCI within 120 minutes and 660 had not. The team found that patients who had received delayed PCI were more likely to be older than those who had received timely PCI (65.0 years versus 62.8 years), female (30.2% versus 24.9%), have diabetes mellitus (19.0% versus 13.9%), and live further away from the primary PCI centre (39.9 km versus 28.6 km).

The unadjusted hazard ratio for the crude all-cause mortality after experiencing STEMI was 1.58 comparing the delayed versus the timely PCI treated patients. The adjusted HR was 1.38 (P=0.006).

"The clock starts at the ECG when the diagnosis is made," Dr Laffan said. "People who got treated beyond the guideline recommended time of 2 hours has a 38% higher chance of being dead" than those who got timely PCI.

STEMI Cases Spike on a Monday

In studying the survival rates of patients with STEMI, Dr Laffan and colleagues have also found that STEMIs are more likely to occur on a Monday than on any other day of the week. 

For this analysis all STEMIs recorded in the Republic of Ireland national acute coronary syndromes database and at both centres providing PCI in Northern Ireland were looked at, again between January 2013 and March 2018. This accounted for 10,528 cases. 

The odds ratio for STEMI occurring on a Monday was 1.13 versus 0.95 on a Tuesday and on a Wednesday, 0.93 on a Thursday, 0.94 on a Friday, 1.0 on a Saturday, and 1.09 on a Sunday. 

"This is just a small sub-analysis, which is just a curiosity," Dr Laffan said, appearing somewhat bemused by the large amount of press coverage that this finding has received as result of its presentation at the BCS meeting. 

"It's a well-known phenomenon," he said, adding that "the same is true for strokes".

Indeed, a meta-analysis performed almost 20 years ago looked into the phenomenon and found that the overall excess risk was small. The authors of that meta-analysis – Professors Adrian Barnett and Annette Dobson who both worked at the University of Queensland in Herston, Australia, at the time – observed that "the excess in coronary events on Mondays is a persistent phenomenon".

They tried to look at possible reasons, from stress through to alcohol consumption and said that "a definitive explanation remains elusive", although there was "some evidence of an association with alcohol consumption".

Dr Laffan noted that the cause was likely multifactorial and that it was reasonable to assume a circadian element based on what has been learned from previous studies.

But is it clinically relevant on which day STEMI occurs? Probably not, he suggested. "It's a spin-off analysis of a clinically important study," referring back to the reduced survival rates of patients who are not revascularized in time.

In a press release issued by the British Heart Foundation (BHF), the charity's Medical Director Professor Sir Nilesh Samani commented on the popularised finding: "Someone is admitted to hospital due to a life-threatening heart attack every five minutes in the UK, so it’s vital that research continues to shed light on how and why heart attacks happen.

"This study adds to evidence around the timing of particularly serious heart attacks, but we now need to unpick what it is about certain days of the week that makes them more likely. Doing so could help doctors better understand this deadly condition so we can save more lives in future."

Neither Dr Laffan nor Professor Sir Samani had any relevant conflicts of interest to disclose.