Coronary flow reserve predicts cardiopulmonary fitness in patients with coronary artery disease independently of systolic and diastolic function

An updated review on therapeutic strategies in coronary microvascular dysfunction

Coronary microvascular dysfunction (CMD) is well-known cause of angina, yet treatment options remain limited. This systematic review and meta-analysis examines the current literature and provides a contemporary evaluation of treatments using a stringent definition for CMD with accurate methods of microvascular assessment in accordance with recent consensus guidelines. Methods and Results: A search strategy was conducted independently by two authors (CK and RR). Studies were required to be prospective trials in adult patients with documented CMD by IC doppler wire, thermodilution techniques, or perfusion imaging via PET/MRI. CMD was defined as either coronary flow reserve (CFR)/myocardial perfusion reserve (MPR) < 2.5, and/or index of microvascular resistance (IMR) > 25. Methodological quality of studies was assessed via the Cochrane Risk of Bias tool. The primary and secondary endpoints were change in CFR/MPR/IMR and change in Seattle Angina Questionnaire (SAQ) scores respectively. Two-sided p-values were used and considered significant if p < 0.05. A total of 11,360 records were identified, from which 14 were included in this review covering 9 different treatments. Two treatments (quinapril and ranolazine) showed significant improvement in both CFR and angina. Three ranolazine trials were pooled in meta-analysis. The standardised mean difference showed a weak positive effect (0.24) with wide intervals (-0.21 to 0.26) which was not statistically significant (p = 0.20). We subsequently reviewed all treatments as mentioned in recent European consensus statements. Conclusions: The overall quality of evidence surrounding treatments for CMD is of "low", with lack of robust data highlighting the dire need for higher quality trials in this area.

Incremental value of non-invasive myocardial work for the evaluation and prediction of coronary microvascular dysfunction in angina with no obstructive coronary artery disease

Background

Evidence suggests that patients suffering from angina with no obstructive coronary artery disease (ANOCA) experience coronary microvascular dysfunction (CMD). We aimed to understand the diagnosis value of noninvasive myocardial work indices (MWIs) with left ventricular pressure-strain loop (LV PSL) by echocardiography in ANOCA patients with CMD.

Methods

97 patients with ANOCA were recruited. All subjects underwent standard echocardiography with traditional ultrasound parameters, two-dimensional speckle-tracking echocardiography with global longitudinal strain (GLS), LV PSL with MWIs include global work index (GWI), global constructive work (GCW), global waste work (GWW) and global work efficiency (GWE). In addition, all enrolled cases underwent high-dose adenosine stress echocardiography (SE) with coronary flow velocity reserve (CFVR). CMD was defined as CFVR <2.0.

Results

Of the 97 patients with ANOCA, 52 were placed in the CMD group and 45 in the control group. GWI and GCW were decreased significantly in the CMD group compared with the control group (P < 0.001 for both). GWI and GCW were moderately correlated with CFVR (r = 0.430, P < 0.001 and r = 0.538, P < 0.001, respectively). In the multiple logistic regression analyses, GCW was identified as the only independent echocardiography parameter associated with CMD after adjusting for age and baseline APV [OR (95%CI) 1.009 (1.005-1.013); P < 0.001]. Moreover, the best predictor of CMD in patients with ANOCA using receiver operating characteristic (ROC) curve was GWI and GCW, with an area under the curve (AUC) of 0.800 and 0.832, sensitivity of 67.3% and 78.8%, specificity of 80.0% and 75.6%, respectively.

Conclusion

MWIs with LV PSL is a new method to detect LV systolic function noninvasively in ANOCA patients with CMD.

Women with coronary microvascular dysfunction and no obstructive coronary artery disease have reduced exercise capacity

BACKGROUND

Both coronary microvascular dysfunction (CMD) and reduced exercise capacity are associated with adverse cardiovascular prognosis. The association between CMD and cardiopulmonary exercise testing (CPET) derived exercise capacity in symptomatic individuals without obstructive coronary artery disease (CAD) is not clear. We investigated whether exercise capacity was reduced in women with angina, CMD and no obstructive CAD compared with sex-matched controls. Furthermore, we assessed the association between CMD and other CPET-derived variables.

METHODS

All participants underwent transthoracic Doppler echocardiography of the left anterior descending artery with dipyridamole-induced vasodilation and CPET using ergometer cycle with an incremental test protocol.

RESULTS

We included 99 women with angina and no obstructive CAD (patients) and 27 asymptomatic women (controls), age (mean ± standard deviation) 61 ± 10 and 58 ± 10 years, respectively. Patients had a higher burden of risk factors compared with controls, while the weekly physical activity level was comparable between the groups (p = 0.72). CMD was present in 27 (27%) patients and 5 (19%) controls. Peak VO₂ was significantly reduced in patients with CMD compared with controls with normal coronary microvascular function ((median (IQR) 17.3 (15.5-21.3) vs. 27.3 (21.6-30.8) ml/kg/min; age-adjusted p = 0.001), independent of cardiovascular risk factors (p = 0.041). Presence of CMD in symptomatic women was also associated with diminished heart rate reserve (p < 0.001) and blunted heart rate recovery.

CONCLUSIONS

Women with angina, CMD and no obstructive CAD have markedly reduced exercise capacity compared with sex-matched controls. Moreover, combination of angina and CMD is associated with impaired heart rate response and heart rate recovery.

Clinical and coronary haemodynamic determinants of recurrent chest pain in patients without obstructive coronary artery disease - A pilot study

BACKGROUND

Coronary haemodynamic testing frequently identifies abnormal pathophysiological parameters in patients with angina and non-obstructed coronaries on angiography (NoCAD) but the clinical utility of these measures has received limited attention.

OBJECTIVE

This study aims to identify the clinical and coronary haemodynamic determinants of recurrent chest pain at one month in patients with NoCAD.

METHODS

Patients with angina, NoCAD (<50% stenosis) and normal LV systolic function underwent invasive coronary haemodynamic testing involving: (1) angiographic TIMI frame and opacification rate, (2) microvascular functional measures including coronary flow reserve (CFR) and hyperaemic microvascular resistance (HMR), (3) coronary endothelial function assessment with low dose intracoronary acetylcholine (IC-ACh) infusions (0.18 μg/min & 1.8 μg/min over 2 min), and (4) Provocative spasm testing with high dose IC-ACh boluses (25, 50 and 100 μg). Clinical and health status were assessed at baseline and one month.

RESULTS

In the 49 NoCAD patients (78% female, mean age of 54 ± 11) undergoing comprehensive coronary haemodynamic testing, 33 (67%) continued to experience chest pain at one month. Determinants of recurrent chest pain on univariate analysis included baseline chest pain status or a HMR > 1.9. Multivariate logistic regression analysis identified frequent angina at baseline (OR: 68.9 [4.1, 1165.0], p = 0.003), previous unstable angina admission (OR: 43.9 [3.5, 547.9], p = 0.003) and a HMR > 1.9 (OR: 15.6 [2.1, 114.0], p = 0.007) as independent predictors of recurrent chest pain.

CONCLUSION

In this small pilot study, an abnormal HMR was the only coronary haemodynamic parameter that was a determinant of ongoing angina at short-term follow-up.

Coronary microvascular dysfunction and myocardial contractile reserve in women with angina and no obstructive coronary artery disease

BACKGROUND

Coronary microvascular dysfunction (CMD) is a potential cause of myocardial ischemia and may affect myocardial function at rest and during stress. We investigated whether CMD was associated with left ventricular diastolic and systolic function at rest and during pharmacologically induced hyperemic stress.

METHODS

In a prospective cohort study, we included 963 women with angina, left ventricular ejection fraction (LVEF) >45%, and an invasive coronary angiogram without significant stenosis (<50%). Parameters of left ventricular diastolic function, LVEF, speckle tracking-derived global longitudinal strain (GLS), and coronary flow velocity reserve (CFVR) were assessed by transthoracic echocardiography at rest and during dipyridamole stress. The GLS and LVEF reserves were defined as the absolute increases in GLS and LVEF during stress.

RESULTS

Coronary flow velocity reserve (CFVR) was measured in 919 women of whom 26% had CMD (defined as CFVR < 2). Coronary microvascular dysfunction (CMD) was associated with higher age and a higher resting heart rate. Women with CMD had a reduced GLS reserve (P = .005), while we found no association between CFVR and LVEF at rest, GLS at rest, or the LVEF reserve, respectively. Global longitudinal strain (GLS) reserve remained associated with CFVR (P = .002) in a multivariable regression analysis adjusted for age, hemodynamic variables, and GLS at rest. In age-adjusted analysis, women with low CFVR had no signs of left ventricular diastolic dysfunction measured by echocardiography at rest.

CONCLUSION

The GLS reserve was significantly lower in women with CMD. The mechanisms underlying the association between CMD and GLS reserve warrant further study.

Coronary flow velocity reserve by echocardiography: feasibility, reproducibility and agreement with PET in overweight and obese patients with stable and revascularized coronary artery disease

Background

Coronary flow velocity reserve (CFVR) measured by transthoracic Doppler echocardiography of the LAD is used to assess microvascular function but validation studies in clinical settings are lacking. We aimed to assess feasibility, reproducibility and agreement with myocardial flow reserve (MFR) measured by PET in overweight and obese patients.

Methods

Participants with revascularized coronary artery disease were examined by CFVR. Subgroups were examined by repeated CFVR (reproducibility) or Rubidium-82-PET (agreement). To account for time variation, results were computed for scans performed within a week (1-week) and for all scans regardless of time gap (total) and to account for scar tissue for patients with and without previous myocardial infarction (MI).

Results

Eighty-six patients with median BMI 30.9 (IQR 29.4–32.9) kg × m⁻² and CFVR 2.29 (1.90–2.63) were included. CFVR was feasible in 83 (97 %) using a contrast agent in 14 %. For reproducibility overall (n = 21) limits of agreement (LOA) were (−0.75;0.71), within-subjects coefficient of variation (CV) 11 %, and reliability 0.84. For reproducibility within 1-week (n = 13) LOA were (−0.33;0.25), within-subjects CV 5 %, and reliability 0.97. Agreement with MFR of the LAD territory (n = 35) was without significant bias and overall LOA were (−1.40;1.46). Agreement was best for examinations performed within 1-week of participants without MI of the LAD-territory (n = 12); LOA = (−0.68;0.88).

Conclusions

CFVR was highly feasible with a good reproducibility on par with other contemporary measures applied in cardiology. Agreement with MFR was acceptable, though discrepancy related to prior MI has to be considered. CFVR of LAD is a valid tool in overweight and obese patients.

Coronary microvascular function, insulin sensitivity and body composition in predicting exercise capacity in overweight patients with coronary artery disease

BACKGROUND

Coronary artery disease (CAD) has a negative impact on exercise capacity. The aim of this study was to determine how coronary microvascular function, glucose metabolism and body composition contribute to exercise capacity in overweight patients with CAD and without diabetes.

METHODS

Sixty-five non-diabetic, overweight patients with stable CAD, BMI 28-40 kg/m(2) and left ventricular ejection fraction (LVEF) above 35 % were recruited. A 3-hour oral glucose tolerance test was used to evaluate glucose metabolism. Peak aerobic exercise capacity (VO2peak) was assessed by a cardiopulmonary exercise test. Body composition was determined by whole body dual-energy X-ray absorptiometry scan and magnetic resonance imaging. Coronary flow reserve (CFR) assessed by transthoracic Doppler echocardiography was used as a measure of microvascular function.

RESULTS

Median BMI was 31.3 and 72 % had impaired glucose tolerance or impaired fasting glucose. VO2peak adjusted for fat free mass was correlated with CFR (r = 0.41, p = 0.0007), LVEF (r = 0.33, p = 0.008) and left ventricular end-diastolic volume (EDV) (r = 0.32, p = 0.01) while it was only weakly linked to measures of glucose metabolism and body composition. CFR, EDV and LVEF remained independent predictors of VO2peak in multivariable regression analysis.

CONCLUSION

The study established CFR, EDV and LVEF as independent predictors of VO2peak in overweight CAD patients with no or only mild functional symptoms and a LVEF > 35 %. Glucose metabolism and body composition had minor impact on VO2peak. The findings suggest that central hemodynamic factors are important in limiting exercise capacity in overweight non-diabetic CAD patients.

Coronary Flow Reserve Predicts Longitudinal Myocardial Deformation Capacity in Heart-Transplanted Patients

AIMS

This study aimed to evaluate the role of microvascular dysfunction on left ventricular (LV) longitudinal deformation, filling pressures, and exercise capacity in heart-transplanted (HTx) patients.

METHODS AND RESULTS

Fifty-seven HTx patients underwent comprehensive echocardiographic graft function assessment during symptom-limited, semisupine exercise test with simultaneous right heart catheterization. Coronary flow velocity reserve (CFVR) was measured in the left anterior descending artery using pulsed Doppler echocardiography. We divided patients into two groups based on upper and lower median of CFVR. Twenty-six healthy subjects served as controls. Compared with healthy controls, HTx patients had reduced CFVR (P < 0.0001), exercise capacity (P < 0.0001), and LV longitudinal deformation capacity (P < 0.0001). HTx patients in the reduced CFVR group (CFVR < 2.73) were more symptomatic (P < 0.0001) and had higher prevalence of coronary cardiac allograft vasculopathy (CAV) (P < 0.0001) than patients in the high CFVR group. Systolic function improved in both HTx groups during exercise. However, LV longitudinal myocardial deformation improved significantly more in the high CFVR group (P < 0.0001). Peak exercise LV global longitudinal strain and CFVR were strongly correlated (r = 0.8, P < 0.0001). A weak correlation was observed between CFVR and invasive cardiac index at peak exercise (r = 0.35, P < 0.01) and CFVR and LV filling measured by E/e' ratio (r = -0.41, P < 0.01) and pulmonary capillary wedge pressure (r = -0.30, P < 0.05).

CONCLUSION

HTx patients have reduced CFVR, exercise capacity, and LV longitudinal myocardial deformation capacity compared with healthy individuals. HTx patients with reduced CFVR are more symptomatic and have increased prevalence of CAV. Furthermore, reduced CFVR is correlated with reduced LV longitudinal myocardial deformation and exercise capacity.

Coronary microvascular function is independently associated with left ventricular filling pressure in patients with type 2 diabetes mellitus

BACKGROUND

Left ventricular (LV) diastolic dysfunction is known as an early marker of myocardial alterations in patients with diabetes. Because microvascular disease has been regarded as an important cause of heart failure or diastolic dysfunction in diabetic patients, we tested the hypothesis that coronary flow reserve (CFR), which reflects coronary microvascular function, is associated with LV diastolic dysfunction in patients with type 2 diabetes.

METHODS

We studied asymptomatic patients with type 2 diabetes but without overt heart failure. Transthoracic Doppler echocardiography was performed that included pulsed tissue Doppler of the mitral annulus and CFR of the left anterior descending artery (induced by adenosine 0.14 mg/kg/min). The ratio of mitral velocity to early diastolic velocity of the mitral annulus (E/e') was used as a surrogate marker of diastolic function. We also evaluated renal function, lipid profile, parameters of glycemic control and other clinical characteristics to determine their association with E/e'. Patients with LV ejection fraction <50%, atrial fibrillation, valvular disease, regional wall motion abnormality, renal failure (serum creatinine >2.0 mg/dl) or type 1 diabetes were excluded. Patients with a CFR <2.0 were also excluded based on the suspicion of significant coronary artery stenosis.

RESULTS

We included 67 asymptomatic patients with type 2 diabetes and 14 non-diabetic controls in the final study population. In univariate analysis, age, presence of hypertension, LV mass index, estimated glomerular filtration rate and CFR were significantly associated with E/e'. Multivariate analysis indicated that both LV mass index and CFR were independently associated with E/e'. In contrast, there were no significant associations between parameters of glycemic control and E/e'.

CONCLUSIONS

CFR was associated with LV filling pressure in patients with type 2 diabetes. This result suggests a possible link between coronary microvascular disease and LV diastolic function in these subjects.

Formula food-reducing diets:A new evidence-based addition to the weight management tool box

The changing pattern of obesity-related disease has created a need for a greater range of weight management options for the increasing number of people for whom weight loss and maintenance cannot be addressed by conventional dietary methods. Formula diet weight loss programmes [very low-calorie diets (VLCDs) (400-800 kcal/day) and low-calorie diets (LCDs) (800-1200 kcal/day)] can deliver weight loss at rates of 1-2 kg/week. This rate of weight loss can result in 10-20 kg weight loss in 8-12 weeks. Many health benefits associated with weight reduction seem to require between 10 and 20 kg weight loss. Formula diet programmes can result in weight loss, reduction of liver volume and reduction of visceral fat before bariatric surgery; weight loss before knee joint replacement surgery has also been shown. The benefit of pre-operative weight loss is still under investigation and such practices before bariatric surgery are variable in surgical units across the UK. Weight loss with formula diet in obesity-associated conditions where inflammation is an important component, such as osteoarthritis and psoriasis, has been demonstrated. Maintenance of about 10% of initial bodyweight loss, with symptom improvement in elderly obese people with knee osteoarthritis, has been shown over a period of 4 years. In obese people with psoriasis, weight loss with skin improvement has been maintained for 1 year. Clinical trials are currently underway to examine the merits of an initial weight loss with formula diet in pre-diabetes, in early type 2 diabetes and in insulin-treated type 2 diabetes. Rapid initial weight loss can result in rapid symptom improvement, such as reduced joint pain in osteoarthritis, improved sleep quality in obstructive sleep apnoea, reduced shortness of breath on exertion, reduced peripheral oedema and rapid improvement in metabolic control in diabetes, all changes that are highly motivating and conducive towards compliance. There is also some evidence for improved vitamin D status and maintained bone health in elderly obese people with osteoarthritis but more research is needed. Rapid initial weight loss was feared to be followed by rapid weight regain. However, provided initial weight loss is delivered in parallel with an intense education programme about nutrition, cooking, shopping and lifestyle for long-term maintenance; and where long-term support is provided, subsequent weight maintenance after VLCDs and LCDs has been shown to be possible. A recent literature review identified high-protein diets, obesity drugs and partial use of formula meal replacements as methods which can result in statistically significantly greater weight maintenance after initial weight loss with VLCDs or LCDs. Anxiety about serious adverse side effects seems to be unfounded although users need to be aware of both minor and more serious, though very infrequent, adverse events, such as gallstones and gallbladder disease.