Relation Between Flow Reserve Capacity of Penetrating Intramyocardial Coronary Arteries and Myocardial Fibrosis in Hypertension: Study Using Transthoracic Doppler Echocardiography

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.

Investigation of the predictive value of speckle tracking imaging for the assessment of cardiac function and clinical prognosis in patients with hypercholesterolemia

The predictive value of speckle tracking imaging (STI) for the assessment of cardiac function and clinical prognosis in patients with hypercholesterolemia was explored. One hundred forty-seven patients with hypercholesterolemia diagnosed in our hospital and 137 healthy adults from our health examination center over the same period were included in this study. Using STI and color Doppler ultrasound, we carried out follow-up of cardiac function in patients with hypercholesterolemia and statistical analysis based on collected data. Global longitudinal strain, global circumferential strain, and the strains of apical long-axis, four-chamber and two-chamber planes, and short-axis mitral valve, short-axis papillary muscle, and short-axis apical levels in the hypercholesterolemia group were significantly lower than those in the control group. Global systolic and early diastolic strain rates were significantly lower than those in the control group. In the coronaries, the percentage of segments with significant differences was 80% (24/30) in the left anterior descending coronary artery (LAD), 66.7% (9/12) in the left circumflex coronary artery (LCX), and 75% (8/12) in the right coronary artery (RCA). The average strains in the long axis, radial, and circumferential directions (Strain_{SL, SC, SR} - Avg) in the three main coronaries were significantly different between the hypercholesterolemia group and control group (P<0.0001). In the three coronaries and their basal and mid segments, there were significant differences between LCX and LAD, and between LCX and RCA (P<0.0001). In conclusion, the application of STI for monitoring cardiac function in patients with hypercholesterolemia provides physicians with useful information related to hypercholesterolemia to achieve early diagnosis and effective treatment.

Scanning Electron Microscopy of Macerated Tissue to Visualize the Extracellular Matrix

Fibrosis is a component of all forms of heart disease regardless of etiology, and while much progress has been made in the field of cardiac matrix biology, there are still major gaps related to how the matrix is formed, how physiological and pathological remodeling differ, and most importantly how matrix dynamics might be manipulated to promote healing and inhibit fibrosis. There is currently no treatment option for controlling, preventing, or reversing cardiac fibrosis. Part of the reason is likely the sheer complexity of cardiac scar formation, such as occurs after myocardial infarction to immediately replace dead or dying cardiomyocytes. The extracellular matrix itself participates in remodeling by activating resident cells and also by helping to guide infiltrating cells to the defunct lesion. The matrix is also a storage locker of sorts for matricellular proteins that are crucial to normal matrix turnover, as well as fibrotic signaling. The matrix has additionally been demonstrated to play an electromechanical role in cardiac tissue. Most techniques for assessing fibrosis are not qualitative in nature, but rather provide quantitative results that are useful for comparing two groups but that do not provide information related to the underlying matrix structure. Highlighted here is a technique for visualizing cardiac matrix ultrastructure. Scanning electron microscopy of decellularized heart tissue reveals striking differences in structure that might otherwise be missed using traditional quantitative research methods.

Association of impaired left ventricular twisting-untwisting with vascular dysfunction, neurohumoral activation and impaired exercise capacity in hypertensive heart disease

AIMS

We investigated the association between left ventricular (LV) torsional deformation and vascular dysfunction, fibrosis, neurohumoral activation, and exercise capacity in patients with normal ejection fraction

METHODS AND RESULTS

In 320 newly-diagnosed untreated hypertensive patients and 160 controls, we measured: pulse wave velocity (PWV); coronary flow reserve (CFR) by Doppler echocardiography; global longitudinal strain and strain rate, peak twisting, the percentage changes between peak twisting, and untwisting at mitral valve opening (%dpTw - UtwMVO ), at peak (%dpTw - UtwPEF ), and the end of early LV diastolic filling (%dpTw - UtwEDF ) by speckle tracking imaging; transforming growth factor (TGFb-1), metalloproteinase-9 (MMP-9), tissue inhibitor of matrix metalloptoteinase-1(TIMP-1), markers of collagen synthesis, and N-terminal pro-brain natriuretic peptide (NT-proBNP). Oxygen consumption (VO2 ), measured by means of cardiopulmonary exercise test, was assessed in a subset of 80 patients. The PWV, CFR, longitudinal strain and strain rate, %dpTw-UtwMVO , %dpTw-UtwPEF , and %dpTw-UtwEDF were impaired in hypertensive patients compared with controls. In multivariable analysis, CFR, PWV, LV mass, and systolic blood pressure were independent determinants of longitudinal strain, strain rate, and untwisting markers (P < 0.05). Increased TGFb-1 was related with increased collagen synthesis markers, TIMP-1 and MMP-9 and these biomarkers were associated with impaired longitudinal systolic strain rate, untwisting markers, CFR and PWV (P < 0.05). Delayed untwisting as assessed by reduced %dpTw - UtwEDF was related with increased NT-proBNP and reduced VO2 (P < 0.05).

CONCLUSIONS

Impaired LV untwisting is associated with increased arterial stiffness and coronary microcirculatory dysfunction, and is linked to reduced exercise capacity and neurohumoral activation in hypertensive heart disease. A fibrotic process may be the common link between vascular dysfunction and abnormal myocardial deformation.

Myofibroblast-mediated mechanisms of pathological remodelling of the heart

The syncytium of cardiomyocytes in the heart is tethered within a matrix composed principally of type I fibrillar collagen. The matrix has diverse mechanical functions that ensure the optimal contractile efficiency of this muscular pump. In the diseased heart, cardiomyocytes are lost to necrotic cell death, and phenotypically transformed fibroblast-like cells-termed 'myofibroblasts'-are activated to initiate a 'reparative' fibrosis. The structural integrity of the myocardium is preserved by this scar tissue, although at the expense of its remodelled architecture, which has increased tissue stiffness and propensity to arrhythmias. A persisting population of activated myofibroblasts turns this fibrous tissue into a living 'secretome' that generates angiotensin II and its type 1 receptor, and fibrogenic growth factors (such as transforming growth factor-β), all of which collectively act as a signal-transducer-effector signalling pathway to type I collagen synthesis and, therefore, fibrosis. Persistent myofibroblasts, and the resultant fibrous tissue they produce, cause progressive adverse myocardial remodelling, a pathological hallmark of the failing heart irrespective of its etiologic origin. Herein, we review relevant cellular, subcellular, and molecular mechanisms integral to cardiac fibrosis and consequent remodelling of atria and ventricles with a heterogeneity in cardiomyocyte size. Signalling pathways that antagonize collagen fibrillogenesis provide novel strategies for cardioprotection.

Coronary flow reserve as a link between diastolic and systolic function and exercise capacity in heart failure

AIMS

In heart failure, a reduced exercise capacity is the prevailing symptom and an important prognostic marker of future outcome. The purpose of the study was to assess the relation of coronary flow reserve (CFR) to diastolic and systolic function in heart failure and to determine which are the limiting factors for exercise capacity.

METHODS AND RESULTS

Forty-seven patients with left ventricular ejection fraction (LVEF) <35 [median LVEF 31 (inter-quartile range 26-34)] underwent cardiorespiratory exercise test with measurement of VO2 peak, a dual X-ray absorptiometry scan for body composition, and a full echocardiography with measurement of LVEF using the biplane Simpson model, mitral inflow velocities, and pulsed wave tissue Doppler. Peak coronary flow velocity (CFV) was measured in the LAD, using pulsed-wave Doppler. CFR was calculated as the ratio between peak CFV at rest and during 2 min of adenosine stress. Fat-free-mass-adjusted VO2 peak correlated significantly with CFR (r = 0.48, P = 0.002), E/e' (r = -0.35, P = 0.02), and s' (r = 0.45, P = 0.001) but not with LVEF (r = 0.23, P = 0.11). CFR correlated significantly with E/e' (r = -0.46, P = 0.003) and s' (r = 0.36, P = 0.02), but not with LVEF (r = 0.18, P = 0.26). When adjusting for CFR in a multivariable linear model, s' but not E/e' remained independently associated with VO2 peak.

CONCLUSION

In this group of heart failure patients, VO2 peak was correlated with CFR, E/e', and s' but not with traditional measures of systolic function. CFR remained associated with VO2 peak independently of diastolic and systolic function and is likely to be a limiting factor in functional capacity of heart failure patients.

Association of abnormal coronary microcirculatory function with impaired response of longitudinal left ventricular function during adenosine stress echocardiography in untreated hypertensive patients

AIMS

Coronary microcirculation is disturbed in hypertensive patients. We investigated the association of coronary flow reserve (CFR) with the response of left ventricular (LV) function as assessed by tissue Doppler imaging (TDI) during adenosine stress echocardiography in never-treated hypertensive patients.

METHODS AND RESULTS

We studied 90 hypertensive patients and 30 control subjects, matched for age and sex, by adenosine stress echocardiography. We measured: (i) CFR, E and A Doppler, S', E', A' mitral annulus velocities with TDI, as well as the E'/A' ratio and the E/E' ratio before and during adenosine infusion (ii) the %changes of the measured indices between baseline and adenosine infusion. After adenosine infusion, there was an increase in S', E', and A' in all patients and controls (P < 0.05). Compared with controls and patients with CFR ≥ 2.5, patients with CFR <2.5 showed a smaller increase in S' (28.6 vs. 30.0 vs. 11.1%, F for interaction = 14.592) and E' (33.3 vs. 33.3 vs.1.5%, F = 28.927) as well as a decrease in E'/A' (9.2 vs. 6.4% vs. -20.0%, F = 5.128) and an increase in E/E' (-6.1 vs. -1.6 vs. 30.5%. F = 12.780) after adenosine infusion (P < 0.05 for all comparisons). CFR was independently related to %changes of TDI parameters (regression coefficient b = 0.576 for S'; b = 0.517 for E'; b = 0.473 for E'/A'; b = -0.520 for E/E', respectively, P < 0.001). By the receiver operating curve, a CFR <2.5 predicted the median changes of all measured TDI markers, with a sensitivity and specificity over 70% (AUC >75%, P < 0.05).

CONCLUSION

An abnormal response of the LV longitudinal function during adenosine stress echocardiography is related to impaired CFR in untreated hypertensive patients.

Coronary flow reserve is a comprehensive indicator of cardiovascular risk factors in subjects with chest pain and normal coronary angiogram

BACKGROUND

The aim of the present study was to analyze the parameters related to baseline coronary flow velocity (CFV) and coronary flow reserve (CFR) using Doppler transthoracic echocardiography (TTE), and to assess their associations with components of the Framingham risk score (FRS), which estimates 10-year risk of coronary heart disease, in subjects with chest pain and a normal coronary angiogram.

METHODS AND RESULTS

A total of 354 individuals (mean age: 55+/-11 years, M:F ratio =186:168) with angina or angina-like chest pain and a normal coronary arteriogram were enrolled. CFR, using TTE and adenosine or dipyridamole, was measured within 2 weeks after coronary angiogram. The clinical, electrocardiographic, echocardiographic and laboratory parameters related to baseline CVF and CFR were analyzed, and CFR was compared with FRS. There was an inverse correlation between baseline CFV and CFR (r=-0.374, P<0.001). On multivariate analysis the fulfilling of left ventricular hypertrophy criteria on electrocardiography was an independent predictor of baseline CFV for the upper 75% quartile (23.2> or =cm/s; odds ratio (OR) = 2.840, 95% confidence interval (CI) =1.155-6.983, P=0.023). On multivariate analysis hemoglobin A(1c) level was independently related to a CFR <2.0 (OR = 2.195, 95%CI = 0.920-1.005, P=0.013). CFR had an inverse correlation with FRS (r=-0.222, P<0.001). On multiple regression analysis among the components of the FRS system (FRSS), independent factors related to a CFR <2.0 included age (OR =1.033, 95%CI =1.000-1.067, P=0.041), high-density lipoprotein-cholesterol level (OR = 0.961, 95%CI = 0.933-0.991, P=0.012) and smoking status (OR = 2.461, 95%CI =1.078-5.618, P=0.033), respectively.

CONCLUSIONS

CFR can be a comprehensive indicator of cardiovascular risk factors, including parameters of the FRSS, in subjects with chest pain and a normal coronary angiogram.

Hypertension and myocardial ischemia

Detailed studies over the past 30 years have built up an impressive evidence base for the presence of myocardial ischemia in patients who have hypertension. This relationship ranges from the obvious association with obstructive coronary artery disease to mechanisms related to hemodynamic, microcirculatory, and neuroendocrine abnormalities. All of these factors serve to destabilize the critical balance between myocardial oxygen supply and demand. We have at our disposal a range of sophisticated investigations that allow us to demonstrate the presence and extent of the ischemia and therefore to target specific therapies to reduce the risk to these patients. Achieving target BP and managing all reversible components of the patient's cardiovascular risk status reduce to a minimum the clinical sequelae of myocardial ischemia in this vulnerable population..

Target organ status in white-coat hypertensives: usefulness of serum procollagen type I propeptide in the respect of left ventricular diastolic dysfunction

BACKGROUND

Myocardial fibrosis is a feature of diastolic dysfunction and target organ damage, which was compared among subjects with normotension (NT), white-coat hypertension (WCH) and essential hypertension (EH). Serum procollagen type I propeptide (PIP) level was assessed as a marker of diastolic dysfunction in WCH.

METHODS AND RESULTS

Of 90 subjects, 30 had NT and 30 had WCH (ambulatory daytime blood pressure <135/85 mmHg) and 30 had EH (untreated mild to moderate hypertension); all underwent biochemical and echocardiographic examinations. Those with WCH had a lower left ventricular (LV) mass index than those with EH, but it was higher than in the NT group. WCH patients had a lower mitral valve E/A ratio and a higher LV E/E' (E': septal mitral annular peak velocity) ratio than NT patients, whereas these values were higher and lower respectively than in the EH group. The LV E/E' ratio, an estimate of LV diastolic function, correlated with the serum PIP concentration in WCH patients (r=0.39, P=0.03).

CONCLUSION

WCH is an intermediate group between NT and EH in respect of target organ damage. These results show a relationship between LV diastolic function and serum PIP in WCH, so the serum PIP level may be a useful marker of diastolic dysfunction and target organ damage in such patients.

Incremental value of pulse wave velocity in the determination of coronary microcirculatory dysfunction in never-treated patients with essential hypertension

BACKGROUND

Coronary microcirculation is disturbed in essential hypertension. We investigated whether arterial stiffness determines coronary flow reserve (CFR) in hypertensive patients.

METHODS

We examined 100 never-treated hypertensives and 20 healthy controls. We measured (i) carotid-to-femoral pulse wave velocity (PWV); (ii) Systolic (V (s)) and diastolic (V (d)) coronary flow velocity, time integral (V (TI)-V (d)) of diastolic velocity and CFR after adenosine by transthoracic echocardiography; (iii) ratio of E wave from mitral inflow to Em of mitral annulus, as an index of left ventricular (LV) diastolic pressures using tissue Doppler; (iv) carotid intima-media thickness (IMT), as an index of vascular damage; and (v) 24-h blood pressure parameters using ambulatory blood pressure monitoring.

RESULTS

Patients had abnormal PWV, IMT, E/Em, resting V (d)/V (s), and CFR than controls (P < 0.05). In hypertensives, PWV was related to abnormal IMT and E/Em which in turn were related to reduced CFR (P < 0.05). PWV and E/Em were independent determinants of CFR and V (d)/V (s) (P < 0.05) in hypertensives. When added to a model including age, sex, smoking, LV mass (LVM), heart rate, 24-h systolic blood pressure (SBP), and E/Em, PWV had an incremental value in the determination of CFR (r (2) change from 0.25 to 0.46, P < 0.01). PWV >10.7 m/s predicted a CFR <2 with 79 and 75% and a CFR <2.6 with 83 and 82% sensitivity and specificity, respectively, using adjusted-receiver operating characteristic curve (ROC) analysis.

CONCLUSIONS

Elevated LV diastolic compressive forces on coronary microcirculation and the presence of generalized vascular damage may explain the association between PWV and CFR. PWV has an incremental value in the determination of impaired coronary microcirculation in hypertensive patients.