Methods of cardiac assessment in IIM
| Methods | Advantages | Disadvantages | Used in IIM |
|---|---|---|---|
| ECG | Can detect ST segment and T wave abnormalities, arrhythmias and conduction abnormalities. May also give indications of left ventricular hypertrophy. Readily available | Some false positive and negative results. Clinical significance often unclear. | Many studies, eg, 6–8 |
| 24 hour ECG/Holter monitoring | Can detect arrhythmias, heart rate variability and ischaemia | Requires more resources than standard ECG | 18 21 70 |
| Echo-cardiography | Can assess wall thickness, size of the four chambers, valve structure, systolic and diastolic function. Strain imaging and tissue doppler are newer methods used to assess cardiac function. | Operator dependent. Low sensitivity for detection of myocardial inflammation and fibrosis | 14–18 21 57 |
| Endomyocardial biopsy | Gold standard for detecting myocardial inflammation and fibrosis. Remains a choice for selected patients based on clinical indication. | Unreliable if patchy lesions. Owing to high risk of complications, biopsies are usually considered unethical in studies | No clinical data in IIM |
| Cardiac MR (CMR) | Can image cardiac structure and function from any projection. Primary imaging modality when diffuse or localised myocardial fibrosis (late gadolinium enhancement or T1 mapping), or myocarditis (T weighted, T1 mapping or early gadolinium enhancement) is suspected. | Time-consuming Requires expensive technology Limited availability | 19 21 67 68 |
| Cardiac 99mTc-PYP scintigraphy | Can detect and quantify inflammation of the myocardium by increased 99mTc-PYP uptake | Requires supplementary CT to image structures. Time-consuming. Limited availability | 18 20 21 |
| CT | Can assess coronary artery calcification (CAC score). Good negative predictive value. | Radiation | 22 |
| Creatine Kinase (CK) | Available and cheap A CK-MB/CK total—ratio >3% usually indicates cardiac damage | In IIM, this ratio might be elevated even without cardiac involvement | 95, used in most IIM studies |
| Troponins Troponin I Troponin T | Serum markers specific to myocardial damage, and are therefore preferred to detect cardiac involvement. Troponin I most specific to the myocardium | Expressed in fetal skeletal muscle and in healthy or regenerating adult skeletal muscle. Both troponin-T and troponin-I can be elevated in the presence of renal failure | 79 95–98 |
| B-type natriuretic peptide (BNP) | Marker of heart failure | Can be elevated in the presence of renal failure | No data in IIM |
IIM, idiopathic inflammatory myopathies.