Universal Definition of Myocardial Infarction, hsTroponin and Clinical Coding of Myocardial Infarction

1. Universal Definition of Myocardial Infarction, hsTroponin and Clinical Coding of Myocardial Infarction Dr John E Macdonald Consultant Cardiologist Salford Royal Foundation Trust

2. Contents Universal definition of MI High sensitivity troponin T assay ICD 10 coding of acute IHD Summary of suggestions/proposals

3. Classification of Acute Myocardial Infarction Type 1: Spontaneous MI related to ischaemia due to a primary coronary event, such as plaque erosion and/or rupture, fissuring, or dissection. Type 2: MI secondary to ischaemia due to an imbalance of O2 supply and demand, as from coronary spasm or embolism, anaemia, arrhythmias, hypertension, or hypotension. Type 3: Sudden cardiac death, with symptoms of ischaemia, accompanied by new ST-segment elevation or LBBB or pathologic or angiographic evidence of fresh coronary thrombus � in the absence of reliable biomarker findings. Type 4a: MI associated with PCI (trop x3 > 99th centile URL). Type 4b: MI associated with verified stent thrombosis. Type 5: MI associated with CABG (trop x5 > 99th centile URL).

4. Criteria for Acute MI Types 1 & 2 Detection of rise and/or fall of cardiac biomarkers (preferably troponin) with at least one value above the 99th percentile of the upper reference limit (for a normal population) together with evidence of ischaemia with at least one of the following: Symptoms of ischaemia. ECG changes of new ischaemia. (new ST changes/new LBBB) or the development of pathological Q waves on the ECG. Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality.

5. Troponin (cTn) Biomarker of choice for the diagnosis of MI as it is the most sensitive and specific biomarker of myocardial injury/necrosis available. The diagnosis of MI should be based on a rising and/or falling pattern of cTn in the appropriate clinical situation. Any type of injury, not just ischaemic injury, can result in cTn release into the bloodstream.

6. High Sensitivity Troponin T Assay Uses same antibodies as 4th generation assay Can accurately measure ten-fold lower levels TnT typically rises substantially in the first 3-6 hours after MI hsTnT assay is more likely to detect a rise early compared with standard TnT assay Recommended to use ng/L units so that results are whole numbers

7. 99th percentile of hs TnT assay

9. hsTnT assay detects an increase in cTnT earlier than the 4th gen. assay

10. Use of hsTnT reclassifies some patients to a diagnosis of NSTEMI from USA

11. Number of TnT tests at SRFT per month (switched to hsTnT Nov)

12. HsTnT - Advantages Earlier diagnosis (detect lower TnT rise earlier after MI) Earlier rule out of MI (not unstable angina) (within 6 hours of admission) Detection of patients with small MIs that may previously have been discharged

13. HsTnT � Possible Disadvantages Less specific for AMI at lower levels (Chronic elevation, other acute aetiologies) Detectable in > 80% of �normals� More referrals to cardiology! (Serial testing imperative to help diagnosis in view of the above issues) More tests, so increased costs (2 or more per patient)

14. Troponin Proposals (Based on current SRFT guidance) Use 99th percentile cut off as recommended in Universal def. as Network Standard for AMI Measure hsTnT at presentation and 6 hours Consider using hsTnT assay (older assays are being withdrawn anyway) For hsTnT use 99th percentile cut off (14ng/L) and rise/fall of 20% if first result >/= 50ng/L (rise/fall of 10ng/L if first result < 50ng/L) for acute myocardial injury consistent with MI

15. Clinical Coding of MI ICD 10 (1990) classification is outdated MI is divided into subendocardial (non-transmural) and transmural with regional description (anterior, inferior or other � posterior, lateral, septal) Subendocardial, transmural and anterior, inferior & post/lat/sept are essential modifiers Coders will not interpret (troponin) results, they will only review the diagnoses made by the clinician (avoid ACS with +/- troponin)

16. ICD 10 Codes for Acute IHD (I20)

17. Lost in Translation The current ICD-10 guidance relating to NSTEMI can be found on page IX-9 of the Clinical Coding Instruction Manual (Version 2.0) and is as follows: �ICD-10 classifies myocardial infarction to the extent of the damage caused to the heart muscle either transmural, non-transmural or unspecified. The terms STEMI and NSTEMI or non-segmented elevation myocardial infarction do not indicate this level of detail and in these instances further clarification needs to be obtained from the clinician. If it is confirmed that a myocardial infarction has occurred and the extent of the damage remains unknown, the appropriate ICD-10 code is I21.9 Acute myocardial infarction unspecified.� ICD-10 revision to come into use within NHS on 1/4/11, but no change to MI coding

18. Squaring the Circle?

19. Implications of MI definition, troponin and coding changes More cardiology referrals! More NSTEMI (subendocardial MI) diagnoses at the expense of unstable angina Possibly more acute cardiac investigations More troponin tests and therefore more spent on diagnostics Hopefully earlier discharge for some Better quality care?

20. Summary of Proposals Use universal definition of MI Use 99th percentile cut off TnT on admission and 6 hours later Change units to ng/L Switch to hs TnT assay Add essential modifiers to diagnoses