Journal and News Scan

Today, The Society of Thoracic Surgeons published the third annual Pediatric Interagency Registry for Mechanical Circulatory Support (PEDIMACS) report. Between Sep 19, 2012 and Dec 31, 2017, 423 patients (less than 19 years of age) in 30 hospitals were supported with 508 devices. The etiology was cardiomyopathy in 261 patients (62%), myocarditis in 48 (11%), congenital heart disease (CHD) in 86 (20%, with 52 of these having single ventricle physiology), and other in 28 (7%). The two most common support strategies included left ventricular assist device in 342 patients (81%) and biventricular assist device (BiVAD) in 64 (15%).

At 6 months, 80% of patients were alive on a device or bridged to transplantation/recovery. Patient characteristics and survival were different among three groups of patients supported with three types of pumps:

1. 197 implantable continuous flow pumps: implant age 13.4 ± 3.8 years, 19% INTERMACS profile 1, 21% intubated at implant, 12% with CHD; 92% alive at 6 months
2. 79 paracorporeal continuous flow (PC) pumps: implant age 3.9 ± 5.2 years, 49% INTERMACS profile 1, 86% intubated at implant, 38% with CHD; 66% alive at 6 months
3. 121 paracorporeal pulsatile pumps: implant age 3.3 ± 3.9 years, 41% INTERMACS profile 1, 77% intubated at implant, 21% with CHD; 77% alive at 6 months

Risk factors for early death were INTERMACS profile 1 (hazard ratio, HR 12.6), BiVAD (HR 3.6), percutaneous devices (HR 13.5), PC pumps (HR 4.1), small volume center (HR 3.3), low age (HR 1.01 for age squared), and low weight (HR 0.9). Intubation (functional capacity, HR 4.3) and liver dysfunction (bilirubin in mg/dL, HR 1.1) at the time of implant were constant hazards.

The investigators conclude that implantable continuous flow pumps are the most common type in children, with greater than 90% survival at 6 months, which may represent the maturation in both patient selection and timing of implantation. Currently paracorporeal continuous flow or pulsatile pumps are limited to supporting most challenging patients, those weighing less than 20 kg, and those with congenital heart defects.

In this statistical primer, Grant and colleagues focus on the use of multivariable regression analyses. The authors review the three most common types of multivariable regression models encountered in the cardiothoracic surgical literature, and they highlight less common models, underscoring the importance of using the correct model for a particular study. They also discuss appropriate approaches for selecting variables and the need to report the model completely so others can reproduce it.

Flynn and colleagues evaluated their center’s implementation of a protocol for extubation within six hours after cardiac surgery, focusing on the rate of adverse events before and after protocol implementation particularly for those patients at highest surgical risk. The authors analyzed prospectively-collected data for patients undergoing cardiac operations within six months of the initiation of the early extubation protocol, 181 patients before and 152 after. They found no differences in the total number of adverse events (renal failure, reintubation, 30-day mortality, or postoperative stroke) before and after the protocol was initiated (16% versus 19%, p = 0.557). In a subset analysis focusing specifically on patients with STS predicted morbidity or mortality score over 40% (8 patients before, 6 patients after the protocol began), the number of adverse events were not different and the median ventilation time was reduced to less than six hours.

The authors conclude that these results are encouraging but merit further investigation, considering the small sample size.

This review summarizes the current understanding of the inherited basis for aortic aneurysmal disease and clearly highlights the need to differentiate between thoracic and abdominal aortic manifestations. Approximately 20% of thoracic aortic aneurysms are associated with an autosomal pattern of inheritance from a mutation in a single gene, whereas abdominal aortic aneurysms (AAAs) do not typically demonstrate such inheritance but rather seem to present as a polygenic disorder involving variants of weaker effect. This notwithstanding, there are some distinct biological pathway similarities between thoracic aortic disease (TAD) and AAA; these include the TGF-β and low-density lipoprotein receptor-related protein (LRP1) pathways, as well as other aspects of vascular smooth muscle cell function.

Currently, over a dozen causative genes have been validated for heritable TAD. Each confers a high risk for disease, and genetic testing for these genes is now offered clinically. The situation is far less advanced for AAA, and although polygenic AAA risk scores are being developed, using genetic variants to predict AAAs has not progressed to the extent that it can be used to identify at-risk individuals.