The challenge of risk stratification in suspected angina, in myocardial infarction without risk factors, and in frail patients

This Focus Issue on ischaemic heart disease contains the Viewpoint article ‘Coronary artery disease in the absence of traditional risk factors: a call for action’ by Suzanne Avis from the University of Tasmania in Australia, and colleagues. The key role of hypertension, hypercholesterolaemia, diabetes mellitus, and smoking in causing coronary artery disease (CAD) has been well recognized at a population level and has been the target of highly effective primary and secondary prevention strategies for >50 years. However, a substantial, and increasing, proportion of patients presenting with lifethreatening acute coronary syndrome (ACS) have none of these standard modifiable cardiovascular risk factors (SMuRFs). Whilst this remains a relatively small proportion of the ‘pie’, the global burden of CAD makes their absolute number substantial, estimated conservatively to impact 29.6 million, and to account for 1.4 million deaths per annum. Despite this, SMuRF-less CAD patients appear to be an invisible group in current clinical trials and guidelines, with little known about their outcomes or the best approach to their management and secondary prevention strategies. Thus, the authors assessed both the European Society of Cardiology and the American College of Cardiology/American Heart Association guidelines to determine the proportion of trials underpinning the guideline recommendations that reported the number or percentage of participants with no SMuRFs. The second Viewpoint article entitled ‘Physical activity and exercise in patients with spontaneous coronary artery dissection and fibromuscular dysplasia’ is by Marysia Tweet from the Mayo Clinic in Rochester, MN, USA, and colleagues. The authors note that spontaneous coronary artery dissection (SCAD) is a nonatherosclerotic aetiology of acute myocardial infarction and sudden cardiac arrest for which research, awareness, and diagnosis have increased substantially over the past 5 years. Co-existent in 45– 86% of SCAD patients, fibromuscular dysplasia (FMD) is a non-atherosclerotic and non-inflammatory disease of the medium and small calibre arteries that is associated with arterial aneurysms, dissections, and stenoses. SCAD recurs in 10–29% of SCAD patients, arterial dissections are reported in up to 28% of FMD patients, and cervical FMD is associated with recurrent spontaneous cervical artery dissections. Risk for future arterial dissections and the safety of physical activity/exercise after a diagnosis of SCAD or FMD is poorly understood. As current recommendations are based on clinical ‘gestalt’ and often an abundance of caution, there is a need for future attention to be focused on this topic in research, and clearly distinguishing between physical activities vs. structured exercise will help to refine recommendations. Further mechanistic research is needed regarding safe cardiorespiratory fitness and strength training thresholds in this patient population. While increased cardiopulmonary fitness is anticipated to be associated with better outcomes, this is not known for SCAD/FMD due to the concern for recurrent arterial dissection or rupture at high exercise intensity levels. As exercise strategies within cardiac rehabilitation continue to be refined, randomized controlled trials of restricted and non-restricted/ facilitated exercise assessing for differences in outcomes such as vascular events, mental health status, and physiological fitness would greatly inform clinical practice. Patients with non-left main coronary bifurcation lesions are usually best treated with a stepwise provisional approach. However, patients with true left main stem bifurcation lesions have been shown in one dedicated randomized study to benefit from systematic dual stent implantation. In a Fast Track clinical research article entitled ‘The European Bifurcation Club Left Main Coronary Stent study: a randomized comparison of stepwise provisional vs.