• myocardial infarction
• cardiac catheterization
• delivery of health care

'In the COVID-19 era…’ is a refrain that, in a few short months, has become one of the most well-worn catchphrases in medical literature, such has been the unprecedented impact of the current pandemic. The imperative to gain an understanding of, and identify treatments for, COVID-19 in a time-critical fashion has brought both the best and worst of medical research to the fore. Expeditious approaches to data dissemination have been adopted, including a surge in data submitted to preprint repositories, while the feasibility of rapid, pragmatic and well-conducted multicentre randomised controlled trials has been amply demonstrated. Conversely, we have seen the potential negative consequences of inaccurate or spurious studies that emerge despite the traditional bastion of peer review. In between these two extremes lie a host of observational data of varying clinical utility.

It is within this middle spectrum that most current studies related to cardiology and COVID-19 reside. It is fair to say that direct cardiac sequelae of COVID-19 were not initially of paramount clinical concern, given that it is primarily a respiratory illness. Latterly, there has been intense debate on social media and in the press regarding the possibility of myocardial involvement, whether this is unique to SARS-CoV-2 infection as opposed to other respiratory viral illnesses, and whether this holds any clinical relevance. Perhaps more quantifiable has been the effect of COVID-19 and subsequent mitigation strategies on the routine workload and case mix of day-to-day acute cardiology, of which myocardial infarction forms a large, and familiar, part. As cardiologists, the management of acute myocardial ischaemia is at the heart of our clinical practice, and urgent invasive management—rightly or wrongly—often takes precedence over other concomitant ailments. At the time of writing, a Pubmed search for articles including the terms ‘COVID-19’ and ‘myocardial infarction’ in the title returned 104 results spanning April–September 2020. Amongst this spate of publications related to the quite specific topic of COVID-19 and myocardial infarction were early data that described potentially worrying trends in acute presentations of ischaemic heart disease. An initial report from 15 centres in Northern Italy, an epicentre of the pandemic, demonstrated a reduction in hospitalisation for acute coronary syndrome in the 6 weeks following the first confirmed case of COVID-19 in Italy, compared with two control periods.1 Similar trends emerged from multiple other countries, including Austria, France, Greece and the USA.2–5 These reports used surveys, regional healthcare system or selected registry data and are thus limited to each individual healthcare setting, but the observations are all concordant, with a downturn in admissions coinciding with the pandemic onset and institution of lockdowns. More comprehensively, English investigators have used routine hospital admission data to provide a national-level overview that is in alignment with other reports, while rolling updates on national cardiovascular accident and emergency presentations from Public Health Scotland tell a similar story.6 7 In addition to overall decreases in acute coronary syndrome admissions, there have also been reports of marked reductions in the rate of ST-segment elevation myocardial infarction (STEMI) cardiac catheterisation laboratory activations and primary percutaneous coronary intervention (PCI).8–10 These consistent trends raise concerns regarding excess morbidity and mortality due to patients avoiding medical attention and receiving late or no treatment for acute myocardial infarction. Alternatively, some degree of true decline in short-term incidence due to the social and lifestyle consequences of lockdown remains plausible.

A limitation of most of these reports is the method of data collection and limited generalisability. In the present study, the authors leverage the power of an established national registry to explore the specific issue of invasive management of myocardial infarction in Sweden during the COVID-19 pandemic.11 Notably, in contrast to many other countries, Sweden has adopted a more liberal strategy during the pandemic, avoiding mandatory lockdown, although of course this does not obviate a voluntary equivalent change in behaviour. Mohammad et al present an analysis of the Swedish Coronary Angiography and Angioplasty registry (SCAAR), which captures coronary angiography and PCI procedures performed in all 29 cardiac catheterisation laboratories in Sweden. They report national data on all patients referred for coronary angiography for myocardial infarction between 1 March and 7 May 2020 and compare this to a cumulative time period spanning the same days in each year from 2015 to 2019. Data linkage provided death data from the National Population Registry up until 16 April 2020.

The main finding was a reduction in the incidence rates of coronary angiography and PCI for myocardial infarction during the pandemic period that was more pronounced in COVID-19 ‘hotspot’ counties and consistent across all patient subgroups, coinciding with rising COVID-19 prevalence. Some small differences in baseline characteristics and in-hospital findings were reported, including slightly less angiographic disease during the pandemic period. There was also a significantly lower rate of coronary artery bypass graft referrals, which could in part reflect pandemic-enforced changes in the decision-making process regarding revascularisation strategies. There was no overall difference in adjusted or unadjusted 7-day mortality between the pandemic and reference periods for the subgroup who had mortality data available. An analysis of Stockholm county, which accounted for >40% of COVID-19 cases, showed a doubling of 7-day mortality for STEMI compared with the reference period despite no difference in time from symptom to PCI or first ECG to PCI, although numbers were small. The authors also report a temporal association between the initiation of a national campaign to raise awareness of myocardial infarction and encourage patients to seek medical attention—a campaign prompted by analysis of national SWEDEHEART registry data, of which SCAAR is a component—and a ‘recovery’ of the incidence of invasive management of myocardial infarction.

Once again, the authors have demonstrated the power of centralised national registries and data linkage, leveraging these resources to deliver a rapid, comprehensive and granular analysis of the effects of the COVID-19 pandemic on invasive management of myocardial infarction in Sweden during the study period. Although direct comparisons with prior reports are fraught due to differences in healthcare settings, data collection and study methodology, the overall theme of a decline in hospital admissions for acute coronary syndromes is undeniable. This study, which focuses only on patients undergoing invasive management but captures all cases at national level, complements the national English data, which included all acute coronary syndrome admissions regardless of management strategy.7 As in other reports, the authors speculate on several possible reasons for the lower incidence observed, but ultimately such uncertainties cannot be resolved within these studies. It would appear, however, that a reluctance to attend hospital due to a fear of contracting COVID-19 may play a role in delayed or deferred presentations. In these circumstances, the rolling data provided from national registries such as these can be powerful tools, guiding the initiation of widespread, specific information campaigns to combat public fear, such as those in Sweden and the UK targeting myocardial infarction awareness.

The present study would be even more informative if overall rates of myocardial infarction admissions and outcomes, rather than only those managed invasively, were available. The authors’ findings should also be taken in context. The importance of this is highlighted by a divergent report of stable rates of invasive management of STEMI in a tertiary centre in New Zealand—an isolated island nation that instituted early lockdown and maintained a low community prevalence of COVID-19, and which stands in contrast to Sweden with regards to population, climate, geography and mitigation strategies.12 Discrepancies with other reports, such as differing rates of reduction between non-ST elevation myocardial infarction and STEMI and differing myocardial infarction case fatality rates, are to be expected given the disparities between studies mentioned above; direct comparisons are not possible.

Nevertheless, the general trend in myocardial infarction during this pandemic is clear. Lower incidences of hospital admissions and invasive management of acute coronary syndromes are concerning and raise the spectre of excess morbidity and mortality due to delayed or absent provision of therapies. This is not to say that a reduction in invasive management specifically is necessarily the dominant concern, as it is well recognised that many coronary interventions for non-ST elevation myocardial infarction do not improve mortality. The delay or absence of the many facets of medical care that are delivered during a hospitalisation for acute coronary syndrome must be considered in totality. There is also no equivocation with regard to the mortality benefit for primary PCI in STEMI. As such, the overall toll to be exacted by the COVID-19 pandemic, both direct and indirect, will be unknown for some time to come. Meanwhile, it remains behoven on the medical community to promote sensible and clinically relevant research and to use the best information available to deliver the best care possible, without engendering a climate of fear and apprehension. More haste, less speed.