Coronary Stents Post CPR

We recently completed an autopsy on a 74 year old patient with a history of congestive heart failure who subsequently experienced myocardial infarction. Stents were placed in the proximal right coronary artery and in the proximal circumflex. Following the procedure the patient experienced vague chest discomfort and then went into asystole while in the CCU, 30 minutes after the stents were inserted. Attempted resuscitation failed.

Autopsy revealed both stents (balloon inflated, non-self expanding) to be collapsed with fractured struts (ie. the wires within the stent mesh framework were broken). Both stents were no longer applied against the coronary artery intima, rather they were sitting freely within the artery lumen. Friable brown material suspicious for thrombus covered both stents making them look like ovoid cigars both in shape and colour. This material was scraped off and showed mostly atheromatous plaque with some admixed fibrinous material of doubtful significance which could represent either thrombus associated with the plaque prior to stenting or perhaps recently acquired. As you can imagine there blood flow would have been very much reduced through these vessels.

Right coronary stent with attached plaque

Circumflex stent with plaque removed

I viewed the angiograms with the cardiologist and the arteries were clearly stenotic and then almost normal in appearance with superb flow following the stenting procedure and then well maintained following removal of the inflating balloon and guide wire. It was beautiful! I cannot explain why the stents should have collapsed. There are a few possible explanations:

1. the stents spontaneously collapsed by themselves (unlikely)

2. the stents were compressed by CPR. This also seems unlikely since one would assume that the arteries would be somehow protected not only by the surrounding soft tissues but also by the calcification within the associated atheromatous plaques.

3. we managed to crush the stents while removing the heart and dissecting the coronary arteries (unlikely).

Non self-expandable stents are well known to collapse due to external pressure, hence such stents are not used in peripheral locations prone to trauma (eg. extremities). I have found a case report which describes a patient with a collapsed stent in the proximal left anterior descending artery following CPR, similar to our patient. The abstract is pasted below. Although I find it unlikely this is the only conclusion that makes any sense. The cause of his asystole remains unexplained since this was pre-CPR and therefore pre-stent compression. Their are other reports both in the literature and anecdotal within our radiology department in which thoracic stents were compressed by CPR. I am surprised this hasn't been reported more often. There isn't much in the literature about this since this paper. I plan to post pictures on my website when they are available.

Here is the abstract

Mechanical Compression of Coronary Artery Stents:

Potential Hazard for Patients Undergoing Cardiopulmonary Resuscitation

Stephan Windecker, MD, Willibald Maier, MD, Franz R. Eberli, MD, Bernhard Meier, MD, and Otto M. Hess,* MD

Mechanical compression of coronary artery stents may be associated with a fatal out- come as the result of refractory myocardial ischemia. We present the history of an 83-yr-old patient, who died owing to hemorrhagic shock 3 days after stent implantation, despite immediate cardiopulmonary resuscitation (CPR). Postmortem examination showed stent compression, probably due to mechanical deformation during CPR. This complication has been reported in two other cases in the literature, suggesting that CPR may be hazardous to patients with coronary artery stents. Cathet. Cardiovasc. Intervent. 51:464–467, 2000.