What is silent myocardial ischemia (SMI)?
It's reduced blood flow to the myocardium in the absence of angina or its symptoms e.g. dyspnea, nausea, diaphoresis, etc. Thus preventing the heart muscle from receiving enough oxygenated blood and the occurrence of myocardial damage.
Causes of SMI:
Diabetes mellitus | Coronary artery disease |
Post-coronary artery bypass surgery | Intensive care unit stay |
Smoking | Sleep apnea |
Diabetes mellitus is one of the most important causes of SMI. In addition to coronary heart disease and dyslipidemia that occur in diabetic patients, autonomic neuropathy is considered the main culprit in developing SMI. Cardiac autonomic neuropathy is defined as the impairment of autonomic control of the cardiovascular system in patients with diabetes after other causes have been excluded. As a result, that would cause elevated pain threshold, which might be high enough to suppress any pain sensation including high-magnitude ischemia.
Methods of diagnosis:
Electrocardiogram and resting echocardiography are two methods of diagnosis. However, history taking and physical examination are the building blocks of diagnosis given the pathology's silent nature. Therefore, patients screened for SMI are usually referred patients with coronary artery disease risk factors or atrial fibrillation or for pre-operative evaluation.
Complications of SMI:
Myocardial infarction, heart failure, valvular dysfunction, arrhythmia and myocardial fibrosis are expected complications in patients with SMI.
Prophylaxis:
SMI is a chronic diabetic complication that occurs in a diabetic patient with poor glycemic control over a long period of time. Consequently, tight glycemic control is the optimal method for prevention of occurrence of the pathology.
Optimal glycemic control is:
Pre-prandial blood glucose | 80-130 mg/dl |
Post-prandial blood glucose | <180 mg/dl |
HbA1c | <7% |
Treatment:
Management of SMI must be tailored according to the patient as he'd usually be diagnosed at an advanced stage. That being the case, medical therapy along with cardiac rehabilitation is efficient for mild cases, while moderate-to-severe cases of ischemia usually require coronary revascularization.
References:
Gul Z, Makaryus AN. Silent Myocardial Ischemia. [Updated 2023 Jan 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK536915/
Verrotti A, Prezioso G, Scattoni R, Chiarelli F. Autonomic neuropathy in diabetes mellitus. Front Endocrinol (Lausanne). 2014 Dec 1;5:205. doi: 10.3389/fendo.2014.00205. PMID: 25520703; PMCID: PMC4249492
Petretta, M., Fiumara, G., Petretta, M.P. et al. Detection of silent myocardial ischemia: Is it clinically relevant?. J. Nucl. Cardiol. 20, 707–710 (2013). https://doi.org/10.1007/s12350-013-9725-z
Hamdan, Mira; Kossaify, Antoine. Silent Myocardial Ischemia Revisited, Another Silent Killer, Emphasis on the Diagnostic Value of Stress Echocardiography with Focused Update and Review. Advanced Biomedical Research 12(1):245, October 2023. | DOI: 10.4103/abr.abr_91_23 Assessed and Endorsed by the MedReport Medical Review Board