Coronary  Embolism and AF

 
Coronary embolism (CE) is a rare  but arguably underdiagnosed phenomenon. This ‘syndrome’ of coronary embolism  with myocardial infarction remains poorly understood primarily due to the lack of  systematic studies. Our understanding of this condition is largely based on autopsy studies and case series. Based on the data from autopsy studies the  incidence of CE is somewhere between 4-13%.(1) The management of acute  myocardial infarction (AMI) has been transformed with the widespread use of  primary PCI. Routine use of primary PCI along with thrombus aspiration (Before  the publications of TASTE and TOTAL trials) gave the perfect opportunity to  explore this poorly understood category of AMI. This month an elegant  retrospective observational analysis of over 2000 index AMI patients screened  for CE was published in Circulation.(1)
 
In this study by Japanese authors,  data on 2,135 consecutive patients with AMI from January 2001 to December 2013  in the Japanese National Cerebral and Cardiovascular Centre (NCVC) AMI database  were analysed. They excluded 359 patients with a history of prior MI (n=241),  PCI (n=90), CABG (n=18), or both PCI and CABG (n=10), leaving a total of 1,776  patients with de novo AMI that were finally analysed. The diagnosis of CE was based on histological, angiographic and intracoronary imaging modalities  including OCT in addition to the clinical features.
 
The authors also proposed a new  set of criteria to define a definite or a probable CE. The three major criteria  included: 1) angiographic evidence of coronary artery embolism and thrombosis  without atherosclerotic components, 2) concomitant multi-site CE, and 3) concomitant systemic embolization excluding left ventricular thrombus due to  AMI. The three minor criteria included: 1) coronary angiography shows < 25%  stenosis, except for the culprit lesion; 2) evidence of an embolic source  detected by any imaging modality; and 3) coexistence of a potential for  thromboembolic disease. Authors proposed that the diagnosis of definite CE be  based on the presence of two or more major criteria, one major criterion plus two or more minor criteria, or three minor criteria. A probable CE if they  fulfilled one major criterion plus one minor criterion or two minor criteria.
 
With application of these robust  criteria, 52 patients were diagnosed with a definite or a probable CE.  Unsurprisingly three quarter of CE patients had either a paroxysmal or permanent AF. Other main causes included valvular heart disease and  cardiomyopathy. Interestingly, CE patients had lower incidence of traditional  risk factors such as hypertension, smoking and dyslipidaemia. Only 39% of  patients with AF were anticoagulated and those who were anticoagulated had  median INR of 1.4 at the time of index CE.
 
After a median FU of 49 months,  10% patients develop recurrent thromboembolism and all were in AF and yet again  mean INR was 1.4 at the time of recurrent event. After a primary CE event, the  five-year rate of recurrent CE or thromboembolism was 8.7% while the five year  MACCE was 27.1%. The median time to a second episode of CE or thromboembolism was 35 months. Authors also performed a propensity score–matched cohort  consisting of 45 patients with CE and 45 patients without CE. Based on this  analysis all-cause mortality (HR, 7.66; 95% CI, 1.65 to 35.45; p<0.001) and  cardiac mortality (HR, 9.29; 95% CI, 1.13 to 76.5; p<0.001) were much higher  in the CE group than in the non-CE group. Authors conclude that the prevalence  of CE in patients with AMI was 2.9% and AF was the most frequent cause. Long-term  outcomes indicate that CE patients represent a high-risk subpopulation of  patients with AMI and therefore require close follow-up.
 
This study highlights the  importance of the role AF plays in the occurrence and prognosis of CE. Previously reports have suggested that AF is independently associated with AMI particularly in women and the blacks.(2, 3)  This is of great concern as incidence of AF is on the rise, which means we are more likely to see a rise in CE as cause of AMI.  There was a distinct underuse of anticoagulation in patients with AF in this  study suggesting that a conscious effort is required to diagnose, risk stratify  and appropriately anticoagulated these high risk AMI patients.(4)

References  and Further Reading(1)
 
  1.         Shibata T, Kawakami S, Noguchi T, Tanaka T, Asaumi Y, Kanaya  T, et al. Prevalence, Clinical Features, and Prognosis of Acute Myocardial  Infarction Due to Coronary Artery Embolism. Circulation. 2015.
  2.         Soliman EZ,  Lopez F, O'Neal WT, Chen LY, Bengtson L, Zhang ZM, et al. Atrial Fibrillation  and Risk of ST-Segment-Elevation Versus Non-ST-Segment-Elevation Myocardial  Infarction: The Atherosclerosis Risk in Communities (ARIC) Study. Circulation.  2015;131(21):1843-50. Epub 2015/04/29.
  3.         Soliman EZ,  Safford MM, Muntner P, Khodneva Y, Dawood FZ, Zakai NA, et al. Atrial  fibrillation and the risk of myocardial infarction. JAMA internal medicine.  2014;174(1):107-14. Epub 2013/11/06.
4.         Niccoli G, Scalone G, Crea  F. Acute myocardial infarction with no obstructive coronary atherosclerosis:  mechanisms and management. European heart journal. 2015;36(8):475-81. Epub  2014/12/21.