Circulation: Clinical Summaries
Original Research Put Into Perspective for the Practicing Clinician
- Electrophysiologic Substrate in Congenital Long QT Syndrome: Noninvasive Mapping With Electrocardiographic Imaging (ECGI)
- Unnatural History of Tetralogy of Fallot: Prospective Follow-Up of 40 Years After Surgical Correction
- Implementation of a Pilot Accountable Care Organization Payment Model and the Use of Discretionary and Nondiscretionary Cardiovascular Care
- What Is the Optimal Chest Compression Depth During Out-of-Hospital Cardiac Arrest Resuscitation of Adult Patients?
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Electrophysiologic Substrate in Congenital Long QT Syndrome: Noninvasive Mapping With Electrocardiographic Imaging (ECGI)
Congenital Long QT syndrome (LQTS) is a hereditary cardiac channelopathy with variable penetrance, which predisposes patients with structurally normal hearts to polymorphic ventricular tachycardia and sudden cardiac death. Although its genetic basis has become well understood, the mechanisms whereby mutations translate to arrhythmia susceptibility in the intact human heart have not been fully defined. The present work is the first to use noninvasive electrocardiographic imaging (ECGI) to map the cardiac electrophysiological substrate in 25 LQTS patients of 4 genetic subgroups. Panoramic mapping with ECGI allowed us to map, with high resolution, the entire ventricular epicardium of the intact heart. The results indicate that the electrophysiological substrate in LQTS is characterized by a long activation–recovery interval (surrogate of local action potential duration) and regions of steep spatial dispersion of repolarization in the ventricular epicardium. The findings support the concept, advanced previously, of reentry as a major mechanism underlying the arrhythmias in LQTS. The location and magnitude of steep gradients varied not only among the genotypes but also among patients with the same genetic mutation. Interestingly, patients who had previous cardiac events also had a significantly steeper dispersion of repolarization compared with asymptomatic patients. Although this observation is preliminary, it could potentially be of clinical relevance. If found to be consistent in a larger prospective study, this could be the basis for noninvasive arrhythmia risk stratification, with ECGI adding to the previously established risk factors. See p 1936.
Unnatural History of Tetralogy of Fallot: Prospective Follow-Up of 40 Years After Surgical Correction
Surgical correction of tetralogy of Fallot has been possible for only ≈50 years. Information on long-term outcome is virtually absent in the literature. This information, however, is of major importance for clinicians involved in the care of these patients and for the patients themselves. Both clinicians and patients would like to know what they can expect and of which late complications they should be aware. Our study provides unbiased information on survival, morbidity, and cardiac function in patients up to 43 years after surgical Fallot correction. Although not normal, survival is quite good, with 86% of the patients who survived the operation alive after 40 years. Ventricular function, both right and left sided, has decreased over time in many patients. There is a gradual increase in tricuspid regurgitation. Functional capacity of the patients is good; the mean maximum workload on bicycle ergometry is 89% of expected, and on the Short Form-36 questionnaire, a tool to measure health perception, patients score equal to or even better than the normal population. However, almost half of the patients have had at least 1 reintervention, mainly pulmonary valve replacement (40%). Patients who had a palliative shunt before correction were more at risk of dying or needing pulmonary valve replacement. Those who had early postoperative arrhythmias were not only more likely to develop late arrhythmias but also had a higher risk for mortality. These new data may contribute to risk stratification and decision making on, for example, prophylactic implantation of a cardioverter-defibrillator. See p 1944.
Implementation of a Pilot Accountable Care Organization Payment Model and the Use of Discretionary and Nondiscretionary Cardiovascular Care
Accountable care organizations (ACOs) seek to reduce growth in healthcare spending while ensuring high-quality care. We hypothesized that ACO implementation would selectively limit the use of discretionary cardiovascular care (defined as care occurring in the absence of indications such as myocardial infarction or stroke) while maintaining high-quality care, such as nondiscretionary cardiovascular imaging and procedures. We compared the use of cardiovascular care before (2002–2004) and after (2005–2009) implementation of a pilot Medicare ACO program, the Physician Group Practice Demonstration. We studied both discretionary and nondiscretionary carotid and coronary imaging and procedures. Our main outcome measure was the difference in the proportion of patients treated with imaging and procedures, among patients of the Physician Group Practice Demonstration practices compared with patients in control practices, before and after Physician Group Practice Demonstration implementation (difference-in-difference). Overall, our analyses found little evidence to suggest that an early ACO Medicare demonstration had any effect on the use of discretionary cardiovascular imaging or revascularization procedures in the intervention groups when compared with matched controls. Our study suggests that better tools and implementation strategies may be necessary to limit the growth in discretionary, specialty-related spending under ACO care contracts. See p 1954.
What Is the Optimal Chest Compression Depth During Out-of-Hospital Cardiac Arrest Resuscitation of Adult Patients?
The 2010 American Heart Association cardiopulmonary resuscitation (CPR) guidelines recommended a CPR compression depth for adults of ≥50 mm (2 in), with no upper limit specified, although this was based on limited human data. This study of 9136 adult out-of-hospital cardiac arrest patients from 9 US and Canadian cities in the Resuscitation Outcomes Consortium found that adequate compression was often not provided, particularly when the compression rate was faster than recommended. The study clearly demonstrated that increased CPR compression depth is strongly associated with better survival to hospital discharge. In addition, however, analyses showed that the maximum survival was observed in the mean depth interval of 40.3 to 55.3 mm (peak, 45.6 mm). Finally, despite a large presumed difference in weight between men and women, their optimal compression depth appeared to be the same. The authors conclude that the 2010 American Heart Association CPR guideline target for compression depth may be too high. They encourage the use of all validated strategies for prehospital and in-hospital cardiac arrest resuscitations to assist rescuers to stay within range for key CPR parameters, including compression depth and rate. See p 1962.
- © 2014 American Heart Association, Inc.
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