Correlation of Platelet Volume Indices with Midterm prognosis in Acute Myocardial infarction with or without ST Elevation

Platelets play a key role in the pathophysiology of acute coronary syndromes (ACS). Many studies have looked in to various characteristics of platelets in patients presenting with ACS. Many of the studies were on platelet count and mean platelet volume. They have clearly established that platelet count is decreased and mean platelet volume is elevated among patients presenting with ACS. The most accepted explanation for this is the consumption of platelets and release of larger and more immature platelets from marrow in to the circulation. According to recent studies larger platelets are enzymatically and metabolically more activeand have a higher potential thrombosis ability compared to smaller ones.The degree of reduction in platelet count and increase in platelet size may denote the extent of platelet consumption and may correlate with the extent of infarction. So these parameters may correlate with both short and long term prognosis after an ACS. Studies have shown conflicting results in this regard. Several studies have shown good correlation of platelet indices with in hospital outcomes, 6 month outcomes as well as 2 year outcomes. But few studies have shown no correlation between platelet indices and 6 month outcome in NSTEACS.The studies looking in to utility of these parameters for prognostication of patients after ACS are absent.

AIMS

1)      To study the correlation of platelet volume indices (mean platelet volume, platelet distribution width and platelet large cell ratio) at the time of presentation with 1 year Major adverse cardiac events among patients with acute myocardial infarction with or without ST elevation.

 2)      To study the serial changes in these indices at three months in patients with abnormal platelet volume indices at presentation and to correlate it with short term major adverse cardiac events.

METHODOLOGY

Study is planned as a prospective cohort study.

Inclusion criteria:

All patients admitted to Calicut medical college in the study period (1 year) with a diagnosis of ST elevation MI or Non ST elevation MI.

ST elevation MI defined as patients with typical chest pain and ECG showing ST elevation. Non ST elevation MI defined as patients with typical chest pain, no ST elevation in ECG and with elevated biochemical markers of cardiac necrosis.

Exclusion criteria:

1.      Patients whose platelet indices could not be estimated within 12 hours of presentation.

2.      Patients with bleeding disorders, preeclampsia, sepsis or with history of recent blood transfusion.

3.      Patients who are receiving drugs which can cause thrombocytopenia.

4.      Patients with recent history of major operation or trauma.

5.      Previous myocardial infarction in 6 months

6.      Severe noncardiac illness limiting survival less than 1year

Baseline evaluation:

Data to be collected regarding demographic characteristics, conventional CAD risk factors, ECG manifestations, Killip class at presentation TIMI score and biochemical values. Before discharge, data to be collected regarding in hospital events, pre discharge Ejection fraction and details of CAG and revascularization if patient has undergone any procedure.

FOLLOW UP

Follow up is planned at one month after discharge then at 3 months and subsequently every 3 months for a period of one year. In patients with any of the three indices abnormal at admission, all the three parameters are repeated at the follow up visit at 3 months. During follow up period, data is to be collected regarding medications, compliance to medications and smoking, details of CAG and revascularization if patient has undergone, mortality and cause of death and clinical events including recurrent acute coronary syndrome, heart failure hospitalizations, hospitalization for documented cardiac arrhythmia

ANALYSIS

Primary outcome:  A composite of death due to any cause, non fatal myocardial infarction and non fatal cerebrovascular accident at one year follow up.

Secondary outcome:

1. In hospital mortality.

2. A Composite of cardiovascular mortality, non fatal MI, hospitalization for heart failure or documented cardiac tachy or bradyarrhythmia in survivors to discharge in the one year follow up period.

Cardiovascular mortality is defined as any unexplained sudden death or in hospital death after admission with a diagnosis of acute coronary syndrome, cardiac failure, cardiacarrhythmia or cerebrovascular accident.

   Each of the platelet indices at admission Mean platelet volume, platelet distribution width and platelet large cell ratio are to be correlated with primary outcome and each of the secondary outcomes.

In patients with any of the indices abnormal at presentation that parameter to be repeated at 3 months and patients are grouped in to those with normalized values and persistently abnormal values. Differences in primary outcome to be analyzed in these two groups.