Acute MI in sickle cell anemia may confer poor outcomes

Ankit A. Desai, MD

The study by Ogunbayo and colleagues addresses an underrecognized and poorly characterized area in the study of sickle cell disease. The idea of trying to better understand the spectrum of ACSs and their presentations in patients with sickle cell disease is a very challenging one.

Deciphering patient symptoms to diagnose an acute MI is already difficult in the general population. Adding to that challenge are patients with sickle cell disease, many of whom have symptoms of chest pain or discomfort from an assortment of noncardiac causes such as musculoskeletal pain. Then, to differentiate those patients at risk for developing or presenting with an acute MI has been a very challenging case when considering a further invasive workup and diagnostic cardiac catherization.

The second difficult topic related to these patient presentations is the type of MI. Is this the traditional plaque rupture event that we think about in an acute MI, or is this something completely different and specific to sickle cell disease and hemolytic anemias? This is further highlighted by published reports that have shown the lack of any macrovascular coronary obstruction or fresh plaque rupture events in a coronary angiogram despite presentation as an acute STEMI on an electrocardiogram. Questions of embolic events and demand-related ischemia have arisen, given the underlying vaso-occlusive and hemolytic pathophysiology of sickle cell disease. Based on these observations, other questions and challenges have also surfaced, including assessment of the true burden of ACS and potential gaps in delivering quality care for patients who have suffered a real acute MI. Additional questions also arise, such as whether traditional medical therapies that we think about for an acute MI should be implemented.

The current article by Ogunbayo and colleagues, for the first time on a much larger scale, addresses the issues of No. 1, what is the prevalence of MIs in patients with of sickle cell disease, No. 2, what is the trend for acute MI occurrence over time of those patients and, No. 3, what are some of the characteristics that define that patient population to better understand what kind of pathophysiology we are dealing with.

In terms of changing actual clinical practice based on the current findings, we must be very careful about implementing anything new, as this is a retrospective review of a national database. Nonetheless, it raises awareness of a critical topic and maybe now we’ll have more investigators interested in more rigorous studies that can ultimately drive changes in medical care for these patients.

It would be important, for example, to be able to look at gaps in care. This article alludes to these patients not getting the same kinds of potential diagnostic tests and therapeutic tests that are typical in a patient with acute MI. Is that a real observation or was that a spurious finding because it is a retrospective national heart review with inherent biases?

If that quality gap exists in failing to deliver appropriate care, what kind of therapy should we be thinking of? One of the issues this article does bring up is that there are multiple types of MIs with different types of therapies we’d consider for different types of MIs. A plaque rupture event would be a very different type of an MI than a non-plaque rupture event.

While I applaud the authors for doing this study of this topic in particular, there are a fair amount of limitations associated with the findings of the study and we have to be very careful about their interpretations.

One additional limitation is we know patients with sickle cell disease get admitted for a whole variety of noncardiac reasons, and several of those reasons are independently associated with poor outcomes. While the authors did a good job of trying to adjust for several of the known variables, with an ICD code, you’re always limited to what you and the care providers entered can adjust for in addition to what you put in for your search term and hence what you can adjust for. Therefore, you have to be careful about whether these outcomes are associated with an acute MI or with the known outcomes that sickle cell patients already have. That is something that needs to be sorted out in future prospective studies.

Ultimately, it’s an interesting observation that’s worth discussing for raising awareness, but we cannot overinterpret it.