Add coronary stent thrombosis to the list of cardiac events influenced by circadian rhythms, with more events occurring during the early morning hours and in a summertime window of late July and early August.
Coronary stent thrombosis joins several other adverse cardiac events that also follow a circadian pattern, such as stroke, unstable angina pectoris, acute myocardial infarction and sudden cardiac death, according to researcher published in JACC: Cardiovascular Interventions.
Most studies that addressed circadian variations in cardiovascular disease were done before the advent of stents, so, researcher from Mayo Clinic-Rochester conducted a retrospective analysis of medical records and the clinic’s registry, finding 124 patients who presented with coronary stent thrombosis between February 1995 and August 2009.
Researchers determined the time of day, day of week, and season of year that the stent thrombosis occurred and recorded when potential triggers were present. In addition, the team categorized each stent thrombosis based on the number of days since the initial stenting procedure: early=0 to 30, late=31 to 360 days, very late=more than 360 days.
The association between the onset of stent thrombosis was lowest at 8 p.m. and highest at 7 a.m. (P=0.006). However, when the team divided the analysis into early, late, and very late stent thrombosis, only the association between early stent thrombosis and time of day remained significant (P=0.030, P=0.537, P=0.096, respectively). Day of week wasn’t associated, but stent thrombosis rates peaked between the end of July and the beginning of August (P=0.036).
In search of potential triggers, the team determined physical activity level before the onset of stent thrombosis in 62 patients. Of these patients, 33.9 percent were sleeping, 25.8 percent were lying or sitting, 29.0 percent were engaged in light-to-moderate physical exertion, and 11.3 percent were engaged in heavy physical exertion. Other medical conditions were also identified as possible triggers among the full 124-patient study sample, including medication noncompliance (5.6 percent), hospitalization for surgery or invasive diagnostics (4 percent), and acute infections (4 percent).
Authors speculated on physiological factors that may contribute to stent thrombosis in the morning hours: Hypercoagulability and hypofibrinolysis; a higher activity level of the renin-angiotensin-aldosterone hormone system between 6 a.m. and 8 a.m., which causes higher blood pressure and heart rate; a higher degree of blood viscosity in the morning, which is magnified by sitting upright after a night of supine sleep; and lowered levels of antithrombotic medication in the morning just before the patient awakens and takes a new dose.
The lack of an association between stent thrombosis and the day of the week is unlike other adverse cardiac events that occur more often on Mondays. Researchers believe that that mental stress from employment plays a more limited role in stent thrombosis. A higher rate of stent thrombosis in the summer months, meanwhile, may be attributed to higher activity levels in warm weather.
While stent thrombosis has decreased in recent years because of dual antiplatelet therapy and improved stent design, researchers said further benefits could result from some simple steps, such as optimizing medical treatment during high-risk periods and taking antithrombotic medication in the evening rather than in the morning to prevent lowest levels of medication during the most hazardous hours.
*This blog post was originally published at ACP Internist*