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In patients with heart failure with reduced ejection fraction, impaired oxygen delivery to peripheral muscles is blunted due to left ventricular systolic dysfunction with a reduced stroke volume reserve during exercise. Hearon and colleagues1 hypothesised that patients with heart failure with preserved ejection fraction (HFpEF) also might have impaired oxygen delivery and utilisation (V02 kinetics) in response to increased skeletal muscle metabolic demands during exercise. In a series of 19 patients with HFpEF, compared to 18 control subjects, there were markedly slower rates of maximal oxygen utilisation due to impaired peripheral oxygen extraction, despite a normal increase in submaximal cardiac output with exercise (figure 1). The authors suggest that impaired peripheral oxygen utilisation might be a target for therapy in patients with HFpEF.
In the aptly titled editorial ‘Package delivered, message not received’, Borlaug2 concludes that ‘there are many steps in the O2 transport pathway that become compromised in people with HFpEF. Hearon and colleagues1 have reminded us how the final steps in this pathway are often just as limiting as the more central steps closer to the heart, and in the process, they have elegantly demonstrated how we may be able to use VO2 kinetics to help identify the patients where these peripheral steps become most compromised (figure 2). If the mail is not being delivered, we need to know why, and the same is true if O2 transport is constrained. It is hoped that with more robust phenotyping methods, using VO2 kinetics and other novel methods, we will one day be in a position to better understand the nature of deficits in both the heart and periphery at the individual patient level, enabling better tailoring of therapies to improve clinical status for this large and ever expanding cohort’.
The diagnosis of acute myocardial infarction (AMI) can be challenging in patients with a left bundle branch block (LBBB) on electrocardiography. Nestelberger and colleagues3 examined the diagnostic performance of ECG criteria and high-sensitivity cardiac troponin (hs-cTn) compared with a centrally adjudicated diagnosis of AMI using the universal definition of myocardial infarction in a series of almost 9000 patients who presented with chest pain. A LBBB was present in <3% of patients and only 30% of these patients had an AMI, with no difference between those with a new or known LBBB. In patients with LBBB, ECG criteria alone were specific (95%–100%), but not sensitive 1%–12%), for diagnosis of AMI. In contrast, a diagnostic algorithm (figure 3) combining ECG criteria with hs-cTn levels at baseline and the change in levels at 1–2 hours, had a high accuracy (97%) for diagnosis of AMI in patients with LBBB.
In an editorial, Glass et al 4 find these results encouraging but caution that ‘these data are limited to patients with suspected AMI due to acute coronary occlusion; at the present time, the algorithm cannot be extrapolated to patients presenting with other possible aetiologies for hs-cTn elevation (eg, troponin elevations due to demand ischaemia, sepsis or renal insufficiency)—this issue is the major limitation of this algorithm. Additionally, in patients with LBBB but without ECG changes diagnostic of AMI, negative hs-cTn determinations should not be construed to preclude the need for further evaluation or treatment of alternative, non-AMI causes of chest pain (eg, unstable angina, pulmonary embolism and so on)’.
Coronary microvascular dysfunction (CMD) increasingly is recognised as a cause of symptoms and predictor of adverse cardiovascular events in the 40% of patients undergoing coronary angiography who are found to have normal vessels or non-obstructive coronary disease. In a comprehensive review article, Rahman and colleagues5 summarise the diagnostic and therapeutic approach to these patients and point out the knowledge gaps needing further clinical research (figure 4).
Other interesting content in this issue includes a review of the clinical presentation and management of pregnancy in women with cardiomyopathy,6 the Education in Heart article on cardiac computed tomographic (CT) imaging (figure 5)7 and the Image Challenge8 case which uses imaging findings to make the diagnosis in 62 year old women with non-sustained ventricular tachycardia.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Commissioned; internally peer reviewed.
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