Assessment of the causal relevance of ECG parameters for risk of atrial fibrillation: A mendelian randomisation study.

BACKGROUND: Atrial electrical and structural remodelling in older individuals with cardiovascular risk factors has been associated with changes in surface electrocardiographic (ECG) parameters (e.g., prolongation of the PR interval) and higher risks of atrial fibrillation (AF). However, it has been difficult to establish whether altered ECG parameters are the cause or a consequence of the myocardial substrate leading to AF. This study aimed to examine the potential causal relevance of ECG parameters on risk of AF using mendelian randomisation (MR). METHODS AND FINDINGS: Weighted genetic scores explaining lifelong differences in P-wave duration, PR interval, and QT interval were constructed, and associations between these ECG scores and risk of AF were estimated among 278,792 UK Biobank participants (mean age: 57 years at recruitment; 19,132 AF cases). The independent genetic variants contributing to each of the separate ECG scores, and their corresponding weights, were based on published genome-wide association studies. In UK Biobank, genetic scores representing a 5 ms longer P-wave duration or PR interval were significantly associated with lower risks of AF (odds ratio [OR] 0.91; 95% confidence interval [CI]: 0.87-0.96, P = 2 × 10-4 and OR 0.94; 95% CI: 0.93-0.96, P = 2 × 10-19, respectively), while longer QT interval was not significantly associated with AF. These effects were independently replicated among a further 17,931 AF cases from the AFGen Consortium. Investigation of potential mechanistic pathways showed that differences in ECG parameters associated with specific ion channel genes had effects on risk of AF consistent with the overall scores, while the overall scores were not associated with changes in left atrial size. Limitations of the study included the inherent assumptions of MR, restriction to individuals of European ancestry, and possible restriction of results to the normal ECG ranges represented in UK Biobank. CONCLUSIONS: In UK Biobank, we observed evidence suggesting a causal relationship between lifelong differences in ECG parameters (particularly PR interval) that reflect longer atrial conduction times and a lower risk of AF. These findings, which appear to be independent of atrial size and concomitant cardiovascular comorbidity, support the relevance of varying mechanisms underpinning AF and indicate that more individualised treatment strategies warrant consideration.

Wearable technology: using Google Glass as a teaching tool.

Wearable technology holds great promise in revolutionising healthcare delivery. The benefits can also be seen in medical education and delivering healthcare in remote places. We report the use of Google Glass technology as a teaching tool in broadcasting a procedure onto a mobile phone as a viewer, replacing expensive and often cumbersome existing equipment.

Sleeping with the fishes: electromagnetic interference causing an inappropriate implantable cardioverter defibrillator shock.

A 60-year-old man with a cardiac defibrillator implanted due to previous ventricular fibrillation arrest and ischaemic cardiomyopathy received a shock while cleaning his fish pond. At the time, his immersed arm was close to a submersed water pump, but the patient was asymptomatic. As a result of the shock he lost consciousness, but collapsed backwards, away from the pond. Interrogation of the device revealed a high-frequency artefact that was sensed by the device and triggered a shock. Device parameters were otherwise normal. Subsequently, the submersed water pump was found to be the source of an external alternating current leak and was identified as the likely cause of the inappropriate shock due to electromagnetic interference (EMI). Awareness of potential sources of EMI along with evaluation of data with a detailed clinical history is warranted in all cases.