Correlations between coronary flow reserve measured with a Doppler guide wire and treadmill exercise testing

A Practical Approach to Invasive Testing in Ischemia with No Obstructive Coronary Arteries (INOCA)

Up to 65% of women and approximately 30% of men have ischemia with no obstructive coronary artery disease (CAD; commonly known as INOCA) on invasive coronary angiography performed for stable angina. INOCA can be due to coronary microvascular dysfunction or coronary vasospasm. Despite the absence of obstructive CAD, those with INOCA have an increased risk of all-cause mortality and adverse outcomes, including recurrent angina and cardiovascular events. These patients often undergo repeat testing, including cardiac catheterization, resulting in lifetime healthcare costs that rival those for obstructive CAD. Patients with INOCA often remain undiagnosed and untreated. This review discusses the symptoms and prognosis of INOCA, offers a systematic approach to the diagnostic evaluation of these patients, and summarizes therapeutic management, including tailored therapy according to underlying pathophysiological mechanisms.

Coronary Microvascular Dysfunction in Rheumatoid Arthritis Compared to Diabetes Mellitus and Association With All-Cause Mortality

OBJECTIVE

Coronary microvascular dysfunction (CMD) is a predictor of cardiac death in diabetes mellitus (DM) independent of traditional cardiovascular (CV) risk factors. Rheumatoid arthritis (RA) is a chronic inflammatory condition, with excess CV risk compared to the general population, in which CMD is hypothesized to play a role; however, there are limited data on CMD in RA and any association with clinical outcomes. The objective of this study was to compare the prevalence of CMD in RA to that in DM and to test the association with all-cause mortality.

METHODS

We performed a retrospective cohort study using data from a registry of all patients undergoing stress myocardial perfusion positron emission tomography as part of routine clinical care from 2006 to 2017. The inclusion criterion was a normal perfusion scan. Patients with RA or DM were classified using previously published approaches. Coronary flow reserve (CFR) was calculated for all patients in the registry and linked with mortality data. CMD was defined as CFR <2.0.

RESULTS

We studied 73 patients with RA and 441 patients with DM. Among patients with a normal perfusion scan, the prevalence of CMD in RA was similar to that in DM (P = 0.2). CMD was associated with increased risk for all-cause mortality in RA (hazard ratio 2.4 [95% confidence interval 1.4-4.2]) as well as increased risk for cardiac-related death at rates similar to those in DM.

CONCLUSION

These findings suggest an important role for CMD as a potential contributor to excess CV risk and mortality in RA, as previously observed in DM, as well as evidence for a mechanistic link between inflammation and cardiovascular disease.

Microvascular Disease, Peripheral Artery Disease, and Amputation

BACKGROUND

The mechanism of adverse limb events associated with peripheral artery disease remains incompletely understood. We investigated whether microvascular disease is associated with amputation in a large cohort of veterans to determine whether microvascular disease diagnosed in any location increases the risk of amputation alone and in concert with peripheral artery disease.

METHODS

Participants in the Veterans Aging Cohort Study were recruited from April 1, 2003 through December 31, 2014. We excluded participants with known prior lower limb amputation. Using time-updated Cox proportional hazards regression, we analyzed the effect of prevalent microvascular disease (retinopathy, neuropathy, and nephropathy) and peripheral artery disease status on the risk of incident amputation events after adjusting for demographics and cardiovascular risk factors.

RESULTS

Among 125 674 veterans without evidence of prior amputation at baseline, the rate of incident amputation over a median of 9.3 years of follow-up was 1.16 per 1000 person-years, yielding a total of 1185 amputations. In time-updated multivariable-adjusted analyses, compared with those without peripheral artery disease or microvascular disease, microvascular disease alone was associated with a 3.7-fold (95% CI, 3.0-4.6) increased risk of amputation; peripheral artery disease alone conferred a 13.9-fold (95% CI, 11.3-17.1) elevated risk of amputation; and the combination of peripheral artery disease and microvascular disease was associated with a 22.7-fold (95% CI, 18.3-28.1) increased risk of amputation.

CONCLUSIONS

Independent of traditional risk factors, the presence of microvascular disease increases the risk of amputation alone and synergistically increases risk in patients with peripheral artery disease. Further research is needed to understand the mechanisms by which this occurs.

Coronary physiology assessment in the catheterization laboratory

Physicians cannot rely solely on the angiographic appearance of epicardial coronary artery stenosis when evaluating patients with myocardial ischemia. Instead, sound knowledge of coronary vascular physiology and of the methods currently available for its characterization can improve the diagnostic and prognostic accuracy of invasive assessment of the coronary circulation, and help improve clinical decision-making. In this article we summarize the current methods available for a thorough assessment of coronary physiology.

Physiological assessment of coronary artery disease in the cardiac catheterization laboratory: a scientific statement from the American Heart Association Committee on Diagnostic and Interventional Cardiac Catheterization, Council on Clinical Cardiology

With advances in technology, the physiological assessment of coronary artery disease in patients in the catheterization laboratory has become increasingly important in both clinical and research applications, but this assessment has evolved without standard nomenclature or techniques of data acquisition and measurement. Some questions regarding the interpretation, application, and outcome related to the results also remain unanswered. Accordingly, this consensus statement was designed to provide the background and evidence about physiological measurements and to describe standard methods for data acquisition and interpretation. The most common uses and support data from numerous clinical studies for the physiological assessment of coronary artery disease in the cardiac catheterization laboratory are reviewed. The goal of this statement is to provide a logical approach to the use of coronary physiological measurements in the catheterization lab to assist both clinicians and investigators in improving patient care.

Electrocardiographic exercise stress testing: an update beyond the ST segment

Routine exercise testing is frequently ordered to evaluate a patient's cardiovascular performance. The test is more direct and less expensive than imaging technology, and derives valuable information. New variables such as dyspnea and heart rate recovery, as well as integrated scores, provide incremental value to conventional analysis of exercise-induced angina or electrocardiographic changes. Considerations relating to test accuracy in women need to be weighed. This paper seeks to make physicians aware of the current status of the test, and improve their understanding of and ability to integrate new variables and scores to more effectively manage their patients.

Coronary flow reserve measurements in hypertension

Taken together, the diagnostic algorithm is leaded by a simple ECG stress test. In case of ST-segment depression the preferred image test should be stress ECG to bring patients at high risk for significant epicardial coronary artery stenosis to coronary angiography (and revascularization). In case of the lack of wall motion abnormalities (during stress-echo test) or absence of epicardial stenosis one may further assess coronary flow reserve with noninvasive Doppler harmonic echocardiography. For ultimate quantitative assessment invasive procedures, such as argon dilution or intracoronary Doppler techniques, represent the appropriate approach. Treatment of microvascular disease may be followed-up by these new noninvasive diagnostic approaches in future and also, at present, by monitoring ST-segment depression.

Intermediate coronary artery stenosis: evidence-based decisions in interventions to avoid the oculostenotic reflex

The prevalence of intermediate coronary artery stenosis (defined as a diameter stenosis of 40% to 70%) is quite large in patients undergoing PTCA. The coronary angiogram is considered the 'gold standard' for the definition of coronary anatomy, in spite of various limitations associated with its use. In recent years, sensor tipped guidewire based methods of physiologic assessment of stenosis severity, like myocardial fractional flow reserve, and poststenotic coronary flow reserve had established their role in the decision making in catheterization laboratory. The decision making should combine morphologic and physiologic assessment as better evidence based approach in guiding therapy to avoid the 'oculostenotic reflex'.

Coronary physiology revisited : practical insights from the cardiac catheterization laboratory

Various coronary physiological measurements can be made in the cardiac catheterization laboratory using sensor-tipped guidewires; they include the measurement of poststenotic absolute coronary flow reserve, the relative coronary flow reserve, and the pressure-derived fractional flow reserve of the myocardium. Ambiguity regarding abnormal microcirculation has been reduced or eliminated with measurements of relative coronary flow reserve and fractional flow reserve. The role of microvascular flow impairment can be separately determined with coronary flow velocity reserve measurements. In addition to lesion assessment before and after intervention, emerging applications of coronary physiology include the determination of physiological responses to new pharmacological agents, such as glycoprotein IIb/IIIa blockers, in patients with acute myocardial infarction. Measurements of coronary physiology in the catheterization laboratory provide objective data that complement angiography for clinical decision-making.

Reduced myocardial flow reserve does not impair exercise capacity in asymptomatic men

We examined whether impaired coronary flow reserve in healthy men is associated with changes in cardiac performance and exercise-induced ischemia. A comparison between 7 asymptomatic men with low flow reserve (<3.5) and 8 men with normal flow reserve (>3.5) showed no differences in these parameters, suggesting that the mechanisms that control myocardial blood flow during exercise remain normal despite the alterations in the mechanisms that control the vasodilatory reaction to dipyridamole.

Assessing the coronary circulation in hypertension

Systemic arterial hypertension is one of the major risk factors for coronary artery disease, coronary microangiopathy, and left ventricular hypertrophy, all of which can potentially lead to cardiac failure and sudden cardiac death. Coronary flow reserve is defined as the maximal increase in coronary flow above its resting, autoregulated level for a given perfusion pressure. In arterial hypertension functional and structural alterations are observed at the level of epicardial vessels as well as in resistive vessels requiring sophisticated approaches to assess coronary flow reserve and thus myocardial perfusion. Electrocardiographic tests and echocardiography can be regarded as monitoring and screening methods. Myocardial scintography is useful to semiquantitatively estimate hypertension-associated perfusion abnormalities, whereas positron emission tomography provides the only quantitative approach of a non-invasive technique for myocardial blood flow measurement. Invasive methods for the assessment of coronary blood flow need cardiac catheterization procedures, such as techniques requiring catheterization of the coronary sinus, angiographic methods, and guidewire based methods. Thermodilution and venous oxymetry in the coronary sinus systematically underestimate coronary flow reserve and are thus considered as only semiquantitative approaches. In contrast, the gas chromatographic argon method allows a quantitative measurement of coronary blood flow at baseline and during maximum vasodilation; thus it is possible to distinguish between an altered autoregulated and maximal flow as the major cause of a reduced coronary flow reserve and to evaluate long-term therapeutic interventions in hypertensive hearts. Videodensitometric and angiographic methods should be restricted only to patients with coronary microangiopathy or with coronary single-vessel disease. Guidewire-based Doppler techniques are suitable to semiquantitatively assess coronary flow reserve with a considerable spatial and time resolution. Myocardial biopsies may gain insight into hypertension-associated structural alterations in small arterioles. Long-term treatment of hypertensive heart disease aims to normalize blood pressure, to reduce left ventricular hypertrophy and to achieve cardioreparation including reversal of the abnormal structure and function of coronary circulation. Based on the different methods for assessment of coronary circulation the therapeutic value of different classes of antihypertensive therapeutics will be evaluated in this overview.

[Methods for coronary functional assessment]

Functional evaluation of coronary vasomotion encompasses the assessment of dynamic changes in coronary lumen, vessel wall, blood flow, intracoronary pressure and myocardial perfusion in response to specific pharmacologic stimuli. These parameters are obtained to characterize mechanisms of physiologic regulation and to evaluate pathophysiologic processes and potential therapeutic strategies, especially with regard to the development of coronary atherosclerosis. To this end, a variety of direct (invasive) and indirect (non-invasive) diagnostic tools are employed. Among the invasive methods are registration of intracoronary Doppler flow, coronary pressure measurements, quantitative coronary angiography and intravascular ultrasound. The non-invasive modalities consist of coronary Doppler echocardiography, positron emission tomography, myocardial scintigraphy and magnetic resonance imaging. Because of the different technical and physiological principles involved, these methods are complementary by providing independent access to different aspects. The combined invasive functional testing as employed in the cardiac catheterization laboratory allows for a simultaneous synopsis of high-resolution coronary imaging and direct measurement of physiologic parameters during local application of defined pharmacologically active substances. However, the demands in terms of equipment, time and operator skills are high and limit this combined invasive approach to specialized centers. Besides these research purposes, a number of functional methods has entered the clinical arena. They are employed to evaluate the hemodynamic significance of coronary lesions and to assess functional outcome of therapeutic interventions in the catheterization laboratory. The underlying principles and applications of the different methods are described and an overview of selected results is presented.