False Electrical Capture in Prehospital Transcutaneous Pacing by Paramedics: A Case Series.

INTRODUCTION: The use of transcutaneous pacing (TCP) for unstable bradycardia has a class 2B recommendation from the American Heart Association. Prior studies have not adequately described the frequency or possible causes of treatment failure. EMS clinicians and leaders have reported false electrical capture as a potential cause. In this study, we aimed to describe the frequency of true electrical capture, documented verification of mechanical capture, and its association with systolic blood pressure (SBP) and survival. METHODS: This was a retrospective study of patients treated by an urban, hospital-based EMS network comprising two EMS agencies between March 2021 and March 2023. Inclusion criteria were adults with a heart rate of <60 bpm and attempted TCP. Variables included: initial electrocardiogram rhythm, SBP, current applied, neurological status at discharge, and diagnosis. The primary outcome was true electrical capture, defined as the presence of a visible wide QRS and T wave. This enabled calculation of false electrical capture. Additional outcomes included change in SBP and neurological status at discharge. RESULTS: 19 of the 23 (82.6%) patients who underwent TCP had false electrical capture despite all 23 having documented mechanical capture by palpated pulse. For patients with true electrical capture, the median change in SBP was +40 mmHg (IQR = 24.25, range= -12 to +49 mmHg). For patients with false electrical capture, the median change in SBP was -1 mmHg (IQR = 58.50, range= -90 to +23 mmHg). Median current for patients with true electrical capture was 95 mA (IQR = 13.75, range = 85-110) versus 70 mA (IQR = 30, range = 55-160) in those with false electrical capture. 16 (69.6%) had outcome data available. Patients with true electrical capture and outcome data (n = 2) survived to admission but only one survived to discharge with good functional capacity. Of 14 with false electrical capture and outcome data, 10 (71.4%) survived to admission; none survived to discharge with functional capacity. CONCLUSIONS: These findings suggest a high proportion of patients undergoing TCP are at risk of false electrical capture despite a recorded palpable pulse. While our analysis is limited to a single EMS network, these data raise concerns regarding the incidence of prehospital false electrical capture. Further research is warranted to calculate the incidence of false electrical capture and evaluate mitigation strategies.

Complex repolarization dynamics in ex vivo human ventricles are independent of the restitution properties.

AIMS: The mechanisms of transition from regular rhythms to ventricular fibrillation (VF) are poorly understood. The concordant to discordant repolarization alternans pathway is extensively studied; however, despite its theoretical centrality, cannot guide ablation. We hypothesize that complex repolarization dynamics, i.e. oscillations in the repolarization phase of action potentials with periods over two of classic alternans, is a marker of electrically unstable substrate, and ablation of these areas has a stabilizing effect and may reduce the risk of VF. To prove the existence of higher-order periodicities in human hearts. METHODS AND RESULTS: We performed optical mapping of explanted human hearts obtained from recipients of heart transplantation at the time of surgery. Signals recorded from the right ventricle endocardial surface were processed to detect global and local repolarization dynamics during rapid pacing. A statistically significant global 1:4 peak was seen in three of six hearts. Local (pixel-wise) analysis revealed the spatially heterogeneous distribution of Periods 4, 6, and 8, with the regional presence of periods greater than two in all the hearts. There was no significant correlation between the underlying restitution properties and the period of each pixel. CONCLUSION: We present evidence of complex higher-order periodicities and the co-existence of such regions with stable non-chaotic areas in ex vivo human hearts. We infer that the oscillation of the calcium cycling machinery is the primary mechanism of higher-order dynamics. These higher-order regions may act as niduses of instability and may provide targets for substrate-based ablation of VF.

Left Ventricular Assist Devices and Pregnancy: Systematic Review of Existing Literature and Case Report.

Although pregnancy is generally contraindicated in advanced heart failure (AHF), successful pregnancies have been observed in patients with left ventricular assist devices (LVADs). The number of pregnancies in patients with LVADs is increasing, yet optimal management strategies remain undefined. Additionally, no successful pregnancies have been reported with the HeartMate 3 (HM3) (Abbott) LVAD. A systematic review of pregnancy in patients with LVADs was prepared utilizing 3 major scientific databases. We also present the first reported case of successful pregnancy and delivery in a patient supported by an HM3 LVAD. The systematic search yielded 95 results. After filtering to include only relevant citations, eight unique cases were identified. Cases were compared on the basis of several clinical factors. Although pregnancies supported by LVADs are medically complex, several cases of successful deliveries have been observed. Clinical management between cases, however, did vary significantly. Several areas requiring further study were identified.

Proceedings of the AST heart allocation meeting at the American Transplant Congress, Philadelphia, Pennsylvania, May 4, 2015.

Ensuring fair and equitable allocation of donor hearts in the US is the charge of the Organ Procurement and Transplantation Network (OPTN). However, the recent increase of candidates waiting without a corresponding increase in available donors, higher waitlist mortality rates in higher status patients, the presence of disadvantaged subgroups, and the changing management of heart failure patients with increased VAD usage, has necessitated review of allocation policy. Therefore, the Heart Subcommittee of the OPTN/UNOS Thoracic Committee is exploring a further-tiered allocation system, devising a "straw man" model as a starting point for modeling analyses and public discussion. On May 4, 2015, an American Society of Transplantation (AST)-endorsed forum to discuss these potential proposed changes took place. Attendees included 41 people, mostly highly experienced transplant cardiologists and cardiothoracic surgeons, representing 19 heart transplant centers across the US, UNOS, and the Scientific Registry of Transplant Recipients (SRTR). There was unanimous agreement that the potential proposed policy will require careful wording to avoid ambiguity and "gaming" of the system, and strong support for abolishment of local organ sharing in favor of geographic sharing. However, contention existed concerning the appropriate prioritization levels of ECMO, temporary VAD/TAH patients as well as the 30-day LVAD listing.