Coronary microvascular dysfunction, arrythmias, and sudden cardiac death: A literature review.

The coronary vascular system has a unique structure and function that is adaptive to myocardial demand. It is composed of a continuous network of vessels receding in size from epicardial arteries to the microvascular circulation. Failure to meet myocardial demand results in ischemia, angina, and adverse myocardial outcomes. It is evident that 50 % of patients with angina have a non-obstructive coronary disease and 66 % of these patients have coronary microvascular dysfunction (CMD). The impact of CMD on the atria and ventricles is exhibited through its association with atrial fibrillation and distortion of ventricular repolarization. Ultimately, this influence increases the risk of mortality, morbidity, and sudden cardiac arrest. CMD serves as an independent risk for atrial fibrillation, increases ventricular electrical inhomogeneity, and contributes to the progression of cardiac disease. The underlying pathogenesis may be attributed to oxidative stress evident through reactive oxygen species, impaired vasoactive function, and structural disorders such as fibrotic changes. Myocardial ischemia, brought about by a demand-supply mismatch in CMD, may create a milieu for ventricular arrythmia and sudden cardiac arrest through distortion of ventricular repolarization parameters such as QT dispersion and corrected QT dispersion.

Post-TAVR conduction abnormalities leading to permanent pacemaker implantation: Risk factors, prevention, and management.

Transcatheter aortic valve replacement (TAVR) often leads to conduction abnormalities, necessitating pacemaker implantation. This review of 38 meta-analyses identified preexisting right bundle branch block (RBBB), LAHB, and new-onset left bundle branch block as key risk factors, with a higher PPM risk in male and older patients. Procedural factors like transfemoral access and self-expandable valves also increase this risk. Prevention focuses on tailoring TAVR to individual electrophysiological and anatomical profiles. However, there's a lack of consensus in managing these conduction disturbances post-TAVR, highlighting the need for further research and standardized treatment strategies.

The Value of Programmed Ventricular Extrastimuli From the Right Ventricular Basal Septum During Supraventricular Tachycardia.

BACKGROUND: The difference between the right ventricular (RV) apical stimulus-atrial electrogram (SA) interval during resetting of supraventricular tachycardia (SVT) versus the ventriculoatrial (VA) interval during SVT (ΔSA-VAapex) is an established technique for discerning SVT mechanisms but is limited by a significant diagnostic overlap. OBJECTIVES: This study hypothesized that the difference between the RV SA interval during resetting of SVTs versus the VA interval during SVTs (ΔSA-VA) would yield a more robust differentiation of atrioventricular nodal re-entrant tachycardia (AVNRT) from atrioventricular reciprocating tachycardia (AVRT) when using the RV basal septal stimulation (ΔSA-VAbase) as compared to the RV apical stimulation (ΔSA-VAapex). Moreover, it was predicted that the ΔSA-VAbase might distinguish septal from free wall accessory pathways (APs) effectively. METHODS: In this prospective study, 105 patients with AVNRTs (age 48 ± 20 years, 44% male) and 130 with AVRTs (age 26 ± 18 years, 54% male) underwent programmed ventricular extrastimuli delivered from both the RV basal septum and RV apex. The ΔSA-VA values were compared between the 2 sites. RESULTS: The ΔSA-VAbase was shorter than the ΔSA-VAapex during AVRT (44 ± 30 ms vs 58 ± 29 ms; P < 0.001), and the opposite occurred during AVNRT (133 ± 31 ms vs 125 ± 25 ms; P = 0.03). A ΔSA-VAbase of ≧85 milliseconds had a sensitivity of 97% and specificity of 96% for identifying AVNRT. Furthermore, a ΔSA-VAbase of 45-85 milliseconds identified AVRT with left free wall APs (sensitivity 86%, specificity 95%), 20-45 milliseconds for posterior septal APs (sensitivity 72%, specificity 96%), and <20 milliseconds for right free wall or anterior/mid septal APs (sensitivity 86%, specificity 98%). CONCLUSIONS: The ΔSA-VAbase during programmed ventricular extrastimuli produced a robust differentiation between AVNRT and AVRT regardless of the AP location with ≧85 milliseconds as an excellent cutoff point. This straightforward technique further allowed localizing 4 general AP sites.

Establishing Safe Working Parameters for Radiofrequency Ablation In Vitro Using Acoustic Sensing, Probability Mapping, and Catheter Contact Angle.

Surgical quality and safety in radiofrequency catheter ablation (RFA) are critical in arrhythmia procedures. Steam pops, in particular, are potentially catastrophic events that must be avoided; otherwise, they may cause significant damage to the myocardium. This study aimed to evaluate the effect of applied RFA inclination angle and tissue contact parameters on the ablated volume and "steam pop" formation. An ex vivo model consisting of a viable ovine myocardium, an ablation catheter, and a circulating warmed 0.9% NaCl saline solution was used. RFA was conducted while controlling for contact force, electrical power, ablation time, flow rate, irrigation, and catheter tip angle. Irrigation was delivered to the catheter tip manually when indicated. Acoustic transducers were included in the setup to detect preliminary acoustic signals. A total dataset of 567 measurements was taken. Benign precursory signals (hissing and lower-intensity "pops") were detected by acoustic sensors preceding the occurrence of "steam pops." Furthermore, a Pearson coefficient of r = 0.809 with P < .01 was shown to exist between the acoustic intensity of a "steam pop" and the ablated lesion volume. RFA powers of 25 and 30 W with a duration of 20 s induced more "steam pops" than ablation powers of ≤20 W with a duration of ≥30 s. There was also an increased probability of "steam pop" formation with the use of a non-irrigated catheter tip, as compared to an irrigated catheter tip. A more acute catheter angle increased the lesion size at powers of 20 and 25 W (r = -0.568 and r = -0.653, both P < .05, respectively). There is a potential benefit of using acoustic sensing as a warning before the occurrence of "steam pops." Varying power, duration, and catheter tip angle will generate different ablation sizes and need to be tailored to individual needs and procedures.

Teaching critical appraisal to large classes of undergraduate medical students using team-based learning versus group discussions: a randomized controlled trial.

BACKGROUND: Evidence on the effectiveness of team-based learning in teaching critical appraisal to large classes of preclinical medical students is scarce. This study investigated whether team-based learning is effective in teaching critical appraisal to large classes of preclinical medical students. METHODS: Between April 2018 and May 2019, 107 first-year medical students were randomly allocated to receive instruction in critical appraisal using team-based learning or traditional group discussions as teaching methods. The primary outcome was students' performance on the Berlin Questionnaire administered at the end of second year. RESULTS: Students' mean (SD) age was 22.0 (0.7) years. Baseline characteristics of the two groups were similar (all p values > 0.05). The mean (SD) Berlin scores of both groups were 80.4 (11.6) and 80.1 (12.1) for team-based learning and group discussions, respectively. Multivariate stepwise linear regression analysis revealed that the student's academic achievement in medical school was the sole predictor of performance on the Berlin Questionnaire (ß = 1.079, p < 0.001), adjusting for gender, Medical College Admission Test score, student's self-reported preferred teaching method, rank upon admission to medical school, score on the Epidemiology and Biostatistics course, and teaching method (team-based learning versus group discussions). CONCLUSIONS: Team-based learning and group discussions were equally effective instructional strategies to teach critical appraisal to large classes of undergraduate medical students. Replication of our findings is needed in other educational settings. TRIAL REGISTRATION: Current Controlled Trials ISRCTN15430424 , retrospectively registered on December 30, 2021.

Patients' and family members' views on pacemaker reuse: An international survey.

INTRODUCTION: The reuse of cardiac implantable electronic devices may help increase access to these therapies in low- and middle-income countries (LMICs). No published data exist regarding the views of patients and family members in LMICs regarding this practice. METHODS AND RESULTS: An article questionnaire eliciting attitudes regarding pacemaker reuse was administered to ambulatory adult patients and patients' family members at outpatient clinics at Centro Nacional Cardiologia in Managua, Nicaragua, Indus Hospital in Karachi, Pakistan, Hospital Carlos Andrade Marín, and Hospital Eugenio Espejo in Quito, Ecuador, and American University of Beirut Medical Center in Beirut, Lebanon. There were 945 responses (Nicaragua - 100; Pakistan - 493; Ecuador - 252; and Lebanon - 100). A majority of respondents agreed or strongly agreed that they would be willing to accept a reused pacemaker if risks were similar to a new device (707, 75%), if there were a higher risk of device failure compared with a new device (584, 70%), or if there were a higher risk of infection compared to a new device (458, 56%). A large majority would be willing to donate their own pacemaker at the time of their death (884, 96%) or the device of a family member (805, 93%). Respondents who were unable to afford a new device were more likely to be willing to accept a reused device (79% vs. 63%, p < .001). CONCLUSIONS: Patients and their family members support the concept of pacemaker reuse for patients who cannot afford new devices.

Exercise-Induced Ventricular Ectopy and Cardiovascular Mortality in Asymptomatic Individuals.

BACKGROUND: The prognosis of exercise-induced premature ventricular contractions (PVCs) in asymptomatic individuals is unclear. OBJECTIVES: This study sought to investigate whether high-grade PVCs during stress testing predict mortality in asymptomatic individuals. METHODS: A cohort of 5,486 asymptomatic individuals who took part in the Lipid Research Clinics prospective cohort had baseline interview, physical examination, blood tests, and underwent Bruce protocol treadmill testing. Adjusted Cox survival models evaluated the association of exercise-induced high-grade PVCs (defined as either frequent (>10 per minute), multifocal, R-on-T type, or ≥2 PVCs in a row) with all-cause and cardiovascular mortality. RESULTS: Mean baseline age was 45.4 ± 10.8 years; 42% were women. During a mean follow-up of 20.2 ± 3.9 years, 840 deaths occurred, including 311 cardiovascular deaths. High-grade PVCs occurred during exercise in 1.8% of individuals, during recovery in 2.4%, and during both in 0.8%. After adjusting for age, sex, diabetes, hypertension, lipids, smoking, body mass index, and family history of premature coronary disease, high-grade PVCs during recovery were associated with cardiovascular mortality (hazard ratio [HR]: 1.82; 95% CI: 1.19-2.79; P = 0.006), which remained significant after further adjusting for exercise duration, heart rate recovery, achieving target heart rate, and ST-segment depression (HR: 1.68; 95% CI: 1.09-2.60; P = 0.020). Results were similar by clinical subgroups. High-grade PVCs occurring during the exercise phase were not associated with increased risk. Recovery PVCs did not improve 20-year cardiovascular mortality risk discrimination beyond clinical variables. CONCLUSIONS: High-grade PVCs occurring during recovery were associated with long-term risk of cardiovascular mortality in asymptomatic individuals, whereas PVCs occurring only during exercise were not associated with increased risk.

The association of cardiovascular mortality with a first-degree family member history of different cardiovascular diseases.

OBJECTIVE: To investigate which history of cardiovascular disease [coronary heart disease (CHD), stroke, or peripheral arterial disease] in a first-degree family member predicts cardiovascular mortality. METHODS: We studied a prospective cohort (the Lipid Research Clinics Prevalence Study) from ten primary care centers across North America. The primary outcome was cardiovascular mortality, assessed using Cox survival models. RESULTS: There were 8,646 participants (mean age: 47.4 ± 12.1 years, 46% women, 52% of participants with hyperlipidemia) who were followed up for a mean duration of 19.4 ± 4.9 years. There were 1,851 deaths (21%), including 852 cardiovascular deaths. A paternal, maternal or sibling history of premature CHD (before 60 years) was present in 26% of participants, of stroke in 27% of participants, and of peripheral arterial disease in 24% of participants. After adjusting for risk factors (age, sex, systolic blood pressure, diastolic blood pressure, body mass index, smoking, fasting glucose, low-density lipoprotein cholesterol and triglycerides), only a paternal history of premature or any CHD, a maternal history of diabetes mellitus or premature or any CHD, and a sibling history of premature CHD, hypertension, or hyperlipidemia were individually predictive of cardiovascular mortality. After adjusting for risk factors and the mentioned familial factors, only paternal and maternal histories of CHD, especially before 60 years, remained predictive of cardiovascular mortality, with a somewhat higher association for a maternal history [adjusted hazard ratio (aHR) = 1.99, 95% CI: 1.36-2.92,P < 0.001 for maternal history of premature CHD; aHR = 1.52, 95% CI: 1.10-2.10, P = 0.011 for paternal history of premature CHD]. Family history of stroke or peripheral arterial disease did not predict cardiovascular mortality. Parental history of premature CHD predicted cardiovascular mortality independently of baseline age (< 60 years and ≥ 60 years), hypertension, or hyperlipidemia and carried more important prognostic value in men rather than women. CONCLUSIONS: In this study, a parental history of CHD, especially before 60 years, best predicted cardiovascular mortality. This finding could help more accurately identify high-risk patients who would benefit from preventive strategies.