This article is more than 5 years old. Information may no longer be current.
Transplant recipients of undersized hearts at greater risk for mortality
Click Here to Manage Email Alerts
Transplant recipients who received undersized hearts or hearts from the opposite sex had an increased risk for mortality at 1 year, according to findings from a new study.
Current protocols for matching donor hearts, which are based on body weight, foster heart-size disparities and may lead to elevated risk, researchers wrote. They suggest that matches be made based on predicted total heart mass instead of body weight.
The retrospective cohort study included 31,634 adult heart transplant pairings from the United Network for Organ Sharing transplantation registry. Using predictive models, researchers calculated the predicted total heart mass for recipient and donor pairs. Then, using those numbers, they assessed organ size mismatch by calculating the percentage difference between donor predicted total heart mass and recipient predicted total heart mass. Donor-recipient pairs were stratified based on that percentage difference.
Undersized hearts led to worse outcomes
According to the results, recipients from the septile of donor-recipient pairs with the most-undersized donor hearts as determined by predicted total heart mass had an elevated risk for mortality within the first year after transplantation (adjusted HR=1.25; P=.03). The researchers found no difference in survival rates across septiles stratified by body-weight differences.
“Contemporary models of [predicted total heart mass] permit the identification of undersized pairings associated with increased risk,” Robert M. Reed, MD, of the University of Maryland School of Medicine, Baltimore, and colleagues wrote. “Specifically, a mismatch involving donor organs with a [predicted total heart mass] greater than 10% to 15% below that of the recipient’s [predicted total heart mass] was associated with a markedly increased risk for mortality. We term this the ‘Grinch effect.’”
Univariate analysis revealed that sex mismatch was associated with higher 1-year mortality rates in male recipients, but not female recipients. However, after adjustment for predicted total heart mass, sex mismatch was associated with higher 1-year mortality rates in female recipients (HR=1.28; P=.02), but not in male recipients (HR=1; P=1).
“Differences in donor-recipient [predicted total heart mass] modulated the survival associated with donor-recipient sex mismatch and identified donor heart undersizing as an otherwise occult and potentially preventable cause of mortality following orthotopic heart transplantation,” the researchers wrote.
Rejection more likely
In other results, recipients with undersized donor hearts were more likely to be treated for acute rejection within 1 year after transplantation, and those with oversized donor hearts were less likely to be treated for rejection.
While the mechanism of action behind why undersized hearts are more likely to fail is unknown, Reed and colleagues suggested it may be associated with high filling pressures.
“After transplantation, the heart exhibits chronotropic incompetence due to denervation as well as diastolic dysfunction,” they wrote. “As such, augmentation of workload depends primarily upon increased stroke volume, which is facilitated chronically through increased filling pressures. These high filling pressures could have particularly pronounced effects in undersized hearts, which likely manifest a relatively greater degree of diastolic dysfunction.”
Since patients with undersized hearts do not have an increased risk for 30-day mortality, the cause is less likely to be an “abrupt perioperative effect” than a “primary mechanism that manifests more gradually,” they wrote.
Disclosure: The researchers report no relevant financial disclosures.
Perspective
Back to Top
Mary Norine Walsh, MD, FACC
The decision that we make at the time of donor-recipient matching is a complex one. It involves blood type, body size and other factors that are specific to each patient. This study will help us make a more informed decision at the time of transplant, in particular in helping to determine if the size of the donor heart is adequate for the recipient. As was stated in the study, undersizing a heart is fraught with difficulties after transplant. What the study has shown us is that compared with simply considering the patient’s weight, using a refined method to assess the size of the heart makes us better able to match the donor and the recipient.
I think the findings will impact clinical practice because of this refinement of the current method of sizing the donor heart with regard to the recipient. However, at the time a donor heart becomes available for a potential heart transplant recipient, many issues including how ill a recipient is and other factors are taken into consideration. If a patient is critically ill, a donor heart that is not the perfect size may be accepted, understanding that long-term outcomes might not be ideal, because that patient may not have another alternative.
It has been known for some time that male recipients of female hearts do more poorly. Undersizing can be a major contributor. The present analysis of size adds to our understanding of this issue, although undersizing is likely not the sole factor in why male recipients do worse with female donors. I’m certain we haven’t gotten to the bottom of that yet.
Click Here to Manage Email Alerts