Convolution Neural Network Algorithm for Shockable Arrhythmia Classification Within a Digitally Connected Automated External Defibrillator.

Background Diagnosis of shockable rhythms leading to defibrillation remains integral to improving out-of-hospital cardiac arrest outcomes. New machine learning techniques have emerged to diagnose arrhythmias on ECGs. In out-of-hospital cardiac arrest, an algorithm within an automated external defibrillator is the major determinant to deliver defibrillation. This study developed and validated the performance of a convolution neural network (CNN) to diagnose shockable arrhythmias within a novel, miniaturized automated external defibrillator. Methods and Results There were 26 464 single-lead ECGs that comprised the study data set. ECGs of 7-s duration were retrospectively adjudicated by 3 physician readers (N=18 total readers). After exclusions (N=1582), ECGs were divided into training (N=23 156), validation (N=721), and test data sets (N=1005). CNN performance to diagnose shockable and nonshockable rhythms was reported with area under the receiver operating characteristic curve analysis, F1, and sensitivity and specificity calculations. The duration for the CNN to output was reported with the algorithm running within the automated external defibrillator. Internal and external validation analyses included CNN performance among arrhythmias, often mistaken for shockable rhythms, and performance among ECGs modified with noise to mimic artifacts. The CNN algorithm achieved an area under the receiver operating characteristic curve of 0.995 (95% CI, 0.990-1.0), sensitivity of 98%, and specificity of 100% to diagnose shockable rhythms. The F1 scores were 0.990 and 0.995 for shockable and nonshockable rhythms, respectively. After input of a 7-s ECG, the CNN generated an output in 383±29 ms (total time of 7.383 s). The CNN outperformed adjudicators in classifying atrial arrhythmias as nonshockable (specificity of 99.3%-98.1%) and was robust against noise artifacts (area under the receiver operating characteristic curve range, 0.871-0.999). Conclusions We demonstrate high diagnostic performance of a CNN algorithm for shockable and nonshockable rhythm arrhythmia classifications within a digitally connected automated external defibrillator. Registration URL: https://clinicaltrials.gov/ct2/show/NCT03662802; Unique identifier: NCT03662802.

Wild type cardiac amyloidosis: is it time to order a nuclear technetium pyrophosphate SPECT imaging study?

Transthyretin (ATTR) amyloidosis is a debilitating systemic disease often associated with symptomatic cardiac involvement. Diagnosis has dramatically changed with the advent of Technetium-99 m pyrophosphate (Tc-PYP) single-photon emission computed tomography (SPECT). With the ability to diagnose ATTR amyloidosis noninvasively and offer newer therapies, it is increasingly important to identify which patients should be referred for this testing. Relative apical sparing of longitudinal strain on echocardiogram can be potentially used to screen such patients. We sought to describe electrocardiogram (ECG) and echocardiogram (TTE) findings, including relative apical sparing of longitudinal strain, in ATTR amyloidosis patients diagnosed non-invasively with 99mTc-PYP imaging. This was a single-center, retrospective study with 64 patients who underwent 99mTc-PYP imaging between June 2016 and February 2019. Relative apical longitudinal strain was calculated from left ventricular longitudinal strain (LV LS) values. No ECG parameters were meaningfully associated with of 99 m Tc-PYP positive patients. LV mass index (p = 0.001), IVSd (p < 0.001), and LVPWd (< 0.001) demonstrated a highly significant difference between positive and negative 99mTc-PYP groups. 99mTc-PYP positive patients had a higher relative apical sparing of LV LS (p < 0.001), and notably, no 99mTc-PYP negative patient had a ratio > 1.0. The finding of relative apical sparing of longitudinal strain can reliably guide clinicians in triaging which patients to consider ordering 99mTc-PYP imaging for the noninvasive diagnosis of wild type cardiac amyloidosis. A patient with clinically suggestive features and an LV LS relative apical sparing ratio > 0.8 can be considered for 99mTc-PYP imaging to evaluate for ATTR cardiac amyloidosis.

A Novel Earbud Detects Aortic Stenosis Murmur Before and After Transcatheter Aortic Valve Replacement.

Noninvasive infrasonic hemodynography using the MindMics earbuds captures low-frequency acoustic vibrations throughout the cardiac cycle. In an n-of-1 analysis, we propose a new method of assessing severe aortic stenosis by using infrasonic hemodynography to detect its characteristic systolic ejection murmur before and after transcatheter aortic valve replacement.

Transcatheter aortic valve replacement: a palliative approach to infective endocarditis.

An 88-year-old man with small lymphocytic lymphoma presented to the hospital with shortness of breath and was diagnosed with heart failure. Serial blood cultures and echocardiography revealed Staphylococcus epidermidis endocarditis, complicated by severe aortic regurgitation. Despite intravenous antibiotic therapy and aggressive intravenous diuresis therapy in the hospital, he decompensated into cardiogenic shock, requiring invasive haemodynamic monitoring and inotrope therapy. With multidisciplinary discussion involving the patient and his children, there was a joint decision that at his advanced age, he would not pursue surgical aortic valve replacement and instead proceed with a transcatheter aortic valve replacement (TAVR) with palliative intent. He underwent TAVR with subsequent symptomatic and functional improvement as well as resolution of cardiogenic shock.

Long-term high-altitude hypoxia influences pulmonary arterial L-type calcium channel-mediated Ca2+ signals and contraction in fetal and adult sheep.

Long-term hypoxia (LTH) has a profound effect on pulmonary arterial vasoconstriction in the fetus and adult. Dysregulation in Ca2+ signaling is important during the development of LTH-induced pulmonary hypertension. In the present study, we tested the hypothesis that L-type Ca2+ channels (CaL), which are voltage dependent and found in smooth, skeletal, and cardiac muscle, are important in the adaptation of pulmonary arterial contractions in postnatal maturation and in response to LTH. Pulmonary arteries were isolated from fetal or adult sheep maintained at low or high altitude (3,801 m) for >100 days. The effects were measured using an L-type Ca2+ channel opener FPL 64176 (FPL) in the presence or absence of an inhibitor, Nifedipine (NIF) on arterial contractions, intracellular Ca2+ oscillations, and ryanodine receptor-driven Ca2+ sparks. FPL induced pulmonary arterial contractions in all groups were sensitive to NIF. However, when compared with 125 mM K+, FPL contractions were greater in fetuses than in adults. FPL reduced Ca2+ oscillations in myocytes of adult but not fetal arteries, independently of altitude. The FPL effects on Ca2+ oscillations were reversed by NIF in myocytes of hypoxic but not normoxic adults. FPL failed to enhance Ca2+ spark frequency and had little impact on spatiotemporal firing characteristics. These data suggest that CaL-dependent contractions are largely uncoupled from intracellular Ca2+ oscillations and the development of Ca2+ sparks. This raises questions regarding the coupling of pulmonary arterial contractility to membrane depolarization, attendant CaL facilitation, and the related associations with the activation of Ca2+ oscillations and Ca2+ sparks.