Background The 2019 coronavirus disease (COVID‐19) has become a global pandemic and the published literature describing the virus has grown exponentially. Methods We conducted a systematic review of the literature to identify the symptoms, comorbidities present, radiological features and outcomes for adults testing positive for COVID‐19 admitted to hospital. The results across multiple studies were numerically pooled to yield total estimated. Results A total of 45 studies were included in this review with 14,358 adult participants (average age 51 years, male 51%). The pooled findings suggest that the most common symptom among patients was fever (81.2%) followed by cough (62.9%), fatigue (38.0%) and anorexia/loss of appetite (33.7%). The comorbidities that were most prevalent among patients with the virus were hypertension (19.1%), cardiovascular disease (17.9%), endocrine disorder (9.3%) and diabetes (9.2%). Abnormal chest X‐ray findings were present in 27.7% of patients and ground‐glass opacity was demonstrated on chest CT in 63.0% of patients. The most frequent adverse outcomes were acute respiratory distress syndrome (27.4%), acute cardiac injury (16.2%) and acute kidney injury (12.6%). Death occurred in 8.2% of patients and 16.3% required intensive care admission and 11.7% had mechanical ventilation. Bacterial or secondary infections affected 8.5% of patients and 6.9% developed shock. Conclusions COVID‐19 most commonly presents with fever, cough, fatigue and anorexia among patients with existing hypertension and cardiovascular disease. It is important as serious adverse outcomes can develop such as acute respiratory distress syndrome, acute cardiac injury, acute kidney injury and death.

Differentiating near-field (NF) and far-field (FF) electrograms (EGMs) is crucial in identifying critical arrhythmogenic substrate during ventricular tachycardia (VT) ablation. A novel algorithm annotates NF-fractionated signals enabling EGM peak frequency (PF) determination using wavelet transformation. This study evaluated the algorithms’ effectiveness in identifying critical components of the VT circuit during substrate mapping. A multicentre, international cohort undergoing VT ablation was investigated. VT activation maps were used to demarcate the isthmus zone (IZ). Offline analysis was performed to evaluate the diagnostic performance of low-voltage area (LVA) PF substrate mapping. A total of 30 patients encompassing 198 935 EGMs were included. The IZ PF was significantly higher in sinus rhythm (SR) compared to right ventricular paced (RVp) substrate maps (234 Hz (195–294) vs. 197 Hz (166–220); P = 0.010). Compared to LVA PF, the IZ PF was significantly higher in both SR and RVp substrate maps (area under curve, AUC: 0.74 and 0.70, respectively). The LVA PF threshold of ≥200 Hz was optimal in SR maps (sensitivity 69%; specificity 64%) and RVp maps (sensitivity 60%; specificity 64%) in identifying the VT isthmus. In amiodarone-treated patients (n = 20), the SR substrate map IZ PF was significantly lower (222 Hz (186–257) vs. 303 Hz (244–375), P = 0.009) compared to amiodarone-naïve patients (n = 10). The ≥200 Hz LVA PF threshold resulted in an 80% freedom from VT with a trend towards reduced ablation lesions and radiofrequency times. LVA PF substrate mapping identifies critical components of the VT circuit with an optimal threshold of ≥200 Hz. Isthmus PF is influenced by chronic amiodarone therapy with lower values observed during RV pacing.

Implantable loop recorders (ILR) are devices that are implanted subcutaneously on the chest, which enables the continuous monitoring of arrhythmias for up to three years. These devices have an important role in helping to make a diagnosis and supporting decisions about the best patient management. There are currently three companies that produce ILRs. The Reveal DX and XT device is produced by Medtronic. The Confirm device is produced by Abbott. The Biomonitor III device is produced by Biotronik. The established indications for ILR include the management of transient loss of consciousness and the diagnosis of undocumented palpitations; however, they are also used for less established applications, including atrial fibrillation (AF) monitoring and risk stratification in patients with previous myocardial infarction or inherited cardiomyopathies. There is also diverse literature exploring the use of these devices in other populations, including patients with conditions such as congenital heart disease, amyloidosis, stroke, obstructive sleep apnea, renal transplant and patients who undergo procedures such as AF ablation and coronary artery bypass graft. In this review, we describe how the use of ILR has been applied in different settings, including patients with cardiac and non-cardiac conditions as well as post-cardiac procedures. We then discuss the potential issues related to using ILR in these other indications.

Functional substrate mapping has emerged as an essential tool for electrophysiologists, overcoming many limitations of conventional mapping techniques and demonstrating favourable long-term outcomes in clinical studies. However, a consensus on the definition of ‘functional substrate’ mapping remains elusive, hindering a structured approach to research in the field. In this review, we highlight the differences between ‘functional mapping’ techniques (which assess tissue response to the ‘electrophysiological stress’ using short coupled extrastimuli) and those highlighting regions of slow conduction during sinus rhythm. We also address fundamental questions, including the optimal degree of electrophysiological stress that best underpins the critical isthmus and the role of wavefront activation in determining the most effective ablation site.

Aims: Accuracy data for non-invasive electrocardiographic imaging (ECGi) in defining the arrhythmogenic substrate for scar-dependent ventricular tachycardia (VT) is lacking. This study evaluated the accuracy of ECGi mapping to localize the arrhythmogenic substrate and assessed the relationship to myocardial scar, isthmus, exit, and successful ablation sites. Methods and results: A total of 48 VTs in 31 patients were mapped with both ECGi (View into Ventricular Onset, VIVO) and electro-anatomical maps (EAM) to define the arrhythmogenic substrate. Myocardial segments were assigned for the VT-exit site region (VT-ESR), isthmus region, successful ablation sites, and cardiac cross-sectional imaging defined scar using the ventricular AHA segment model and underwent blinded analysis. VT-ESR complete match (defined as exact AHA segment concordance between ECGi and EAM) was seen in 67% and partial match (defined as adjacent segments) in 21% of VTs. ECGi VT-ESR was located within or adjacent to cross-sectional imaging defined scar in 85% of VTs. The VT isthmus was within or adjacent to the ECGi VT-ESR in 77% of VTs. Successful ablation sites were within or adjacent to the ECGi VT-ESR in 82% of VTs. VIVO ECGi accuracy was not affected by cardiomyopathy type or VT cycle length. In identifying epicardial VT-ESR for ischaemic cardiomyopathy, VIVO ECGi had a sensitivity and specificity of 71.4% and 92.9%; for non-ischaemic cardiomyopathy 66.7% and 100%, respectively. Conclusion: ECGi mapping with VIVO can accurately predict the arrhythmogenic substrate for scar-dependent VT. Incorporation of ECGi mapping to conventional VT ablation workflows may improve procedural efficiency.

Catheter ablation is the primary treatment for ventricular tachycardia (VT) in patients with structural heart disease. Unfortunately, its long-term success remains limited. Although mapping techniques have advanced considerably, optimal ablation indices remain essential but less well defined. This two-part comprehensive review bridges the gap between bench and bedside by evaluating methods, technologies, and VT-specific lesion parameters. Here, in part 1, we critically examined conventional and emerging techniques, including radiofrequency (RF), high-power short-duration ablation, temperature-controlled RF. In the accompanying paper, part 2, we focus on bipolar RF ablation, pulsed field ablation and ultra-low-temperature cryoablation, venous ethanol and needle ablation. Despite the growing set of tools available for VT operators, clinical data on the practical and safe creation of lesions remain scarce. The evidence supporting most of the techniques reviewed is limited. We emphasise the need for personalised ablation strategies based on substrate and myocardial anatomy and advocate for the development of future integrated, metric-driven technologies.