Microvasculature Implants Are Not Used to Treat Coronary Microvascular Dysfunction
There are no implants placed in the coronary microvasculature for treating CMD—this condition is managed exclusively with medical therapy, lifestyle modifications, and risk factor control. 1, 2
Why Implants Are Not Feasible
The coronary microvasculature consists of vessels <500 micrometers in diameter that are far too small for any device implantation. 3 These vessels represent the vast majority of total coronary circulation and control overall coronary resistance, but their microscopic size makes them inaccessible to interventional procedures. 4
Actual Treatment Approach for CMD
First-Line Medical Therapy
Beta-blockers (such as bisoprolol) are the recommended first-line antianginal therapy for CMD, targeting a resting heart rate of 55-60 beats per minute. 1 The mechanism involves slowing heart rate to increase diastolic time and improve coronary perfusion, which is particularly important given the microvascular dysfunction. 1
However, ivabradine may be superior to beta-blockers in head-to-head comparison, demonstrating better effects on coronary collateral flow and coronary flow reserve despite achieving similar heart rate reduction. 1
Treatment Algorithm
Baseline therapy for all patients: Aspirin, statin, and ACE inhibitor, plus sublingual nitroglycerin as needed 1
Heart rate control: Start with beta-blocker (or ivabradine as potentially superior alternative) 1
If inadequate response or intolerance: Substitute non-dihydropyridine calcium channel blockers (diltiazem or verapamil) 1
For refractory symptoms: Add ranolazine (particularly useful in microvascular spasm, diabetes, or low blood pressure) 1
Additional options: Trimetazidine as add-on therapy 1
For enhanced pain perception: Adenosine antagonists or tricyclic antidepressants 1
Critical Contraindications
Never use beta-blockers if vasospastic angina is present, as they can precipitate spasm by leaving α-mediated vasoconstriction unopposed. 1 Also contraindicated in second-degree or higher AV block, severe peripheral artery disease, or critical limb ischemia. 1
Diagnostic Confirmation Required
Proper diagnosis using invasive coronary function testing or non-invasive assessment (PET, cardiac MRI, or transthoracic Doppler) is essential before initiating CMD-specific therapy. 2 Key diagnostic thresholds include CFR <2.0-2.5 and IMR ≥25 units. 2
Prognosis and Importance
CMD carries a 2.5% annual risk of adverse cardiac events including myocardial infarction, stroke, heart failure, and death—this is not a benign condition. 5 The diagnosis is more common in women (41% prevalence in selected patients without obstructive CAD) and confers worse prognosis than originally recognized. 2
What About Epicardial Coronary Interventions?
While percutaneous coronary intervention (PCI) with stent placement is used for obstructive epicardial coronary disease, 3 these interventions target large epicardial vessels, not the microvasculature. Recent evidence confirms PCI provides angina relief compared to placebo in stable angina with ischemia, 3 but this applies only to obstructive epicardial disease, not CMD.