Post-MI Mechanical Complications Infrequent but Deadly

Though mechanical complications after acute MI are now rare in the United States, they’re still associated with abysmal outcomes in the contemporary era, particularly in patients with STEMI, new data show.

Among more than 9 million hospitalizations for acute MI, the rate of mechanical complications—papillary muscle rupture, ventricular septal defect, and free wall rupture—was 0.27% in STEMI and 0.06% in NSTEMI, with no significant changes in those figures over the nearly 13-year study period.

In-hospital mortality rates associated with these complications were high—42.4% in STEMI and 18.0% in NSTEMI. Those didn’t change over time either.

“In order to reduce the incidence of these complications, efforts should be directed towards increasing the awareness of the public to avoid delays in presentation so effective therapies can be administrated promptly,” study author Islam Elgendy, MD (Massachusetts General Hospital, Boston, MA), told TCTMD in an email.

Moreover, he said, “the early identification of the patients with mechanical complications and transferring them to tertiary centers with surgical backup, and the involvement of multidisciplinary shock teams in these patients, might help to improve the outcomes.”

Senior author Hani Jneid, MD (Baylor College of Medicine and Michael E. DeBakey VA Medical Center, Houston, TX), added in an email: “Our efforts should be directed towards identifying effective measures to improve the prognosis in these patients.”

The study, with lead author Ayman Elbadawi, MD (University of Texas Medical Branch at Galveston), was published online today ahead of the September 23, 2019, issue of JACC: Cardiovascular Interventions.

Lack of Improvement in Recent Years

Prior research has shown that even though the emergence of reperfusion therapies drastically cut the occurrence of mechanical complications after acute MI, these events remained associated with poor outcomes. There are limited data, however, from the era of more advanced interventional techniques and adjunctive therapies.

For this study, the investigators examined data from the National Inpatient Sample on hospitalizations for acute MI from 2003 to September 2015. The analysis included more than 3.95 million STEMIs and 5.11 million NSTEMIs.

During the study period, rates of all three mechanical complications held steady both in STEMI and NSTEMI. Asked about that lack of improvement, Jneid said that it could be related to advancements in imaging used to detect the complications and greater awareness of them among treating physicians. “Therefore, the rates of mechanical complications in the earlier years of the analysis might have been underestimated,” he said. “Thus, we observed no change.”

As for why in-hospital mortality stayed stubbornly high among patients who developed a complication despite improvements in overall acute MI outcomes, Elgendy noted that “patients who develop mechanical complications usually suffer an extensive infarction and present late. Once these complications occur, surgery is usually the only therapeutic modality,” which can be a problem because these patients are very sick.

After multivariate adjustment, the researchers confirmed that patients with versus without mechanical complications had heightened risks of in-hospital mortality (particularly among women with STEMI and patients older than 75), cardiogenic shock, acute kidney injury, hemodialysis, and respiratory complications. Complications were also associated with greater use of mechanical circulatory support and longer lengths of stay.

Several predictors of mortality were identified, but after propensity-score matching, receipt of cardiac surgery remained as a factor associated with a lower risk of dying in the hospital after STEMI (OR 0.43; 95% CI 0.37-0.52) and NSTEMI (OR 0.31; 95% CI 0.21-0.43).

“This could be a result of the salubrious effects of surgical repair but may also reflect the fact that the more critically ill patients with mechanical complications were more likely not to undergo surgical intervention,” the authors say.

Better Postoperative Support Needed?

Commenting for TCTMD, Roberto Lorusso, MD, PhD (Maastricht University Medical Center, the Netherlands), said there is not much information about post-MI mechanical complications in contemporary practice, which is one of the reasons he and his colleagues are conducting the CAUTION study. This is a retrospective, multicenter, international effort to look into the outcomes of patients who underwent surgery for mechanical complications that developed after acute MI.

Lorusso said he expects the results of the retrospective phase to be available by the end of the year. “I think that we will have a better screenshot of what is happening around the world, but we believe that we will find the same result as shown by the paper published [by Elbadawi et al], which is high in-hospital mortality and no trend [toward] positive change along the most recent years.” For him, the in-hospital mortality rate exceeding 40% among STEMI patients with mechanical complications is “unacceptable” and “a remarkable negative result.”

To start moving mortality rates lower, Lorusso said patient management needs to be changed and, in particular, those undergoing surgery to correct complications probably need to be supported with mechanical circulatory support devices more because they are often in shock, have acidosis, and have a heavy burden of comorbidities. “We should be a little bit more aggressive in supporting these patients in the delicate phase, which is the perioperative phase,” he said.

Lorusso acknowledged that that is a hypothesis not currently supported by evidence. But, he said he hopes that the findings from the retrospective phase of the CAUTION study will help inform a prospective study to confirm or refute the benefits of more aggressive circulatory support around the time of surgery.

Of note, in the study by Elbadawi et al, use of mechanical circulatory support was not associated with improved outcomes in patients with mechanical complications. “However,” Elgendy noted, “the study design does not allow [us] to understand whether this is related to the lack of benefit from these devices or if this is related to the fact that the sicker patients received these therapies.”

In an accompanying editorial, Herbert Aronow, MD, and Chirag Bavishi, MD (both Brown University, Providence, RI), say registries like CAUTION may help inform practice.

Nonetheless, “prevention is the ideal management strategy for mechanical complications post-MI,” they write. “The American Heart Association Mission: Lifeline aims to address the timeliness of reperfusion therapy in STEMI and to reduce symptom-to-balloon time and first medical contact-to-device time. Efforts focused on earlier recognition of MI, minimizing prehospital and in-hospital procedural delays, and use of fibrinolysis when these cannot be overcome may be the best hope to prevent development of these complications and thereby improve overall outcomes post-MI.”