Microvascular Angina - Long-Term Exercise Stress Test Follow-up

Echocardiographic assessment of primary microvascular angina and primary coronary microvascular dysfunction

There is an increasing interest in the role of echocardiography in the evaluation of primary microvascular angina, which is attributed to primary coronary microvascular dysfunction. Valid echocardiographic techniques are expected to facilitate the diagnosis and follow-up of these patients and would be valuable for research purposes and therapy evaluation. However, adequate echocardiographic data are lacking, and the interpretation of the limited available literature is hindered by the previous addition of microvascular angina under more inclusive entities, such as cardiac syndrome X. In experienced hands, the assessment of primary coronary microvascular dysfunction in patients with suspected primary microvascular angina, using multiple echocardiographic techniques is feasible, relatively inexpensive, and safe. Exclusion of obstructive epicardial coronary artery disease is, however, a prerequisite for diagnosis. Two-dimensional transthoracic echocardiography, routine stress echocardiography, and speckle-tracking echocardiography indirectly assess primary coronary microvascular dysfunction by evaluating potential impairment in myocardial function and lack diagnostic sensitivity and specificity. Conversely, certain echocardiographic techniques, including Doppler-derived coronary flow velocity reserve and myocardial contrast echocardiography, assess some coronary microvascular dysfunction parameters and have exhibited diagnostic and prognostic potentials. Doppler-derived coronary flow velocity reserve is the best studied and only guideline-approved echocardiographic technique for documenting coronary microvascular dysfunction in patients with suspected microvascular angina. Myocardial contrast echocardiography, by comparison, can detect heterogeneous and patchy myocardial involvement by coronary microvascular dysfunction, which is an advantage over the common practice of coronary flow velocity reserve assessment in a single vessel (commonly the left anterior descending artery) which only reflects regional microvascular function. However, there is no consensus regarding the diagnostic criteria, and expertise performing this technique is limited. Echocardiography remains underexplored and inadequately utilized in the setting of microvascular angina and coronary microvascular dysfunction. Appraisal of the current echocardiographic literature regarding coronary microvascular dysfunction and microvascular angina is important to stay current with the progress in its clinical recognition and create a basis for future research and technological advancements.

Results of bicycle exercise stress test in patients with stable coronary heart disease depending on the angiographic signs of atherosclerotic lesions of coronary arteries

The aim. To identify features of exercise response in coronary heart disease (CHD) patients depending on coronary artery condition and to identify factors associated with a positive test in patients with no obstructive coronary artery disease (INOCA). Materials and methods. The study included 105 patients diagnosed with stable coronary artery disease (CAD) who were hospitalized at the City Clinical Hospital No. 8 of the Kharkiv City Council. The criteria for diagnosis of ischemia with no obstructive coronary artery disease (INOCA) were met by 53 patients who formed group I. Group II included 52 patients who were consistently hospitalized in the period from June to December 2020, and had obstructive CAD for more than 50 % according to their coronary angiography (CAG). Results. According to the results of bicycle exercise stress test, a positive test was significantly more often registered in group II – n=30 (57.7 %) patients compared to group I – n=19 (35.8 %) patients (p=0.0249). The duration of the test in patients of group I was significantly longer than 420 seconds [290–540], compared with group II – 300.0 [210.0–540.0] (р=0.0352). Also, in patients in group II, the maximum volume of the test performed was probably lower than in group I (p=0.0324). When calculating the double product, it was also found that in group I its value was significantly higher compared to group II (p=0.0292). In group I there was a significantly higher rate of chronotropic reserve (44.0 [26.0–60.0]), compared with group II (p=0.0168). Elevated total cholesterol (above 5 mmol/l) is a statistically significant and independent factor of a positive exercise test in patients with INOCA (OR, 1.98 [0.9992-3.926], p=0.05). A correlation was found between the level of exercise tolerance and smoking in INOCA-patients (r =-0.388975, p=0.010899). Patients who underwent MINOCA also showed reduced tolerance to exercise (r=-0.3104, p=0.042721) Conclusions. The sensitivity of bicycle exercise stress test in patients with CAD depends on the presence and severity of atherosclerotic lesions of the coronary arteries (63 % in stenotic atherosclerosis, 36 % in no obstructive coronary arteries. It was found that exercise test duration, double product, chronotropic and inotropic reserve of the heart in patients with a positive exercise test with INOCA were significantly higher compared with patients with obstructive CAD. Independent factors associated with a positive exercise test in patients with no obstructive CAD are an increase in total cholesterol (multivariate regression logistic analysis).

Association of High Density Cholesterol With Hyperemic Epicardial Flow and Frame Count Reserve in Patients With Moderate Coronary Lesions and Slow Coronary Flow

Background

Patients with microvascular angina and non-obstructive coronary atherosclerotic disease have an elevated risk of adverse events and all-cause mortality compared with individuals without ischaemic heart disease. The diagnosis coronary microvascular dysfunction in this setting relies on the detection of impaired coronary flow at rest or on calculation of coronary flow reserve. Previous studies demonstrate that the coronary flow reserve assessed by the corrected thrombolysis in myocardial infarction method - the frame count reserve is an objective quantitative alternative to other widely used invasive methods for microvascular status evaluation.

Purpose

We assessed the significance of clinical, hemodynamic, angiographic variables and therapy with reference to FCR in a small group of patients with up to moderate atherosclerotic coronary lesions and slow coronary flow. Materials and methods: Frame count reserve was evaluated in 15 patients without flow-limiting (>50%) coronary stenoses admitted with unstable angina. Frame count reserve was calculated by dividing the baseline corrected thrombolysis in myocardial infarction frame count (cTFC) by the cTFC assessed after intracoronary infusion of 100 µg of the calcium channel blocker - verapamil.

Results

The values of frame count reserve correlate positively with the levels of high density cholesterol (r= 0.900, p=0.001), inversely coronary flow after the application of verapamil - cTFCv (r= - 0.534, p=0.049). cTFCv was positively related with the levels of high density lipoproteins (r = - 0.645; p= 0.044) and was negatively influenced by the presence of atherosclerotic lesions at quantitative angiography (42.8±19.1 (n=8) vs 23±5.4 (n=7), p=0.029).The therapy with β-blocker and long-acting nitrate was associated with insignificantly higher frame count reserves after intracoronary verapamil compared to the continuous intake only of β-blocker or β-blocker and verapamil (2.1±0.78 vs 1.34±0.14 vs 1.70±0.70, p=NS).

Conclusions

Higher high-density lipoproteins relate to higher frame count reserves evaluated using verapamil. The improved blood flow after this microvascular vasodilator is consistently positively related to high-density cholesterol and the lack of atherosclerosis at conventional coronary angiography. The combined intake of micro- and macrovascular vasodilator could be associated with higher frame count reserves compared to therapy with β-blocker and one vasodilating drug.