Coronary flow and resistance reserve in patients with chronic aortic regurgitation, angina pectoris and normal coronary arteries

Model-based analysis of the sensitivities and diagnostic implications of FFR and CFR under various pathological conditions

Although fractional flow reserve (FFR) and coronary flow reserve (CFR) are both frequently used to assess the functional severity of coronary artery stenosis, discordant results of diagnosis between FFR and CFR in some patient cohorts have been reported. In the present study, a computational model was employed to quantify the impacts of various pathophysiological factors on FFR and CFR. In addition, a hyperemic myocardial ischemic index (HMIx) was proposed as a reference for comparing the diagnostic performances of FFR and CFR. Obtained results showed that CFR was more susceptible than FFR to the influence of many pathophysiological factors unrelated to coronary artery stenosis. In particular, the numerical study proved that increasing hyperemic coronary microvascular resistance significantly elevated FFR while reducing CFR despite fixed severity of coronary artery stenosis, whereas introducing aortic valve disease only caused a significant decrease in CFR with little influence on FFR. These results provided theoretical evidence for explaining some clinical observations, such as the increased risk of discordant diagnostic results between FFR and CFR in patients with increased hyperemic microvascular resistance, and significant increase in CFR after surgical relief of severe aortic valve disease. When evaluated with respect to the predictive value for hyperemic myocardial ischemia, the performance of FFR was found to be considerably compromised in the presence of severe coronary vasodilation dysfunction or aortic valve disease, whereas the relationship between CFR and HMIx remained relatively stable, suggesting that CFR may be a more reliable indicator of myocardial ischemia under complex pathophysiological conditions.

Echocardiographic assessment of coronary microvascular dysfunction: Basic concepts, technical aspects, and clinical settings

Coronary flow reserve is the capacity of the coronary circulation to augment the blood flow in response an increase in myocardial metabolic demands and has a powerful prognostic significance in different clinical situations. It might assess with invasive and noninvasive technique. Transthoracic echocardiography Doppler is an emerging diagnostic technique, noninvasive, highly feasible, safe for patient and physician, without radiation, and able to detect macrovascular and microvascular anomalies in the coronary circulation. This review aims to describe the benefit and limits of echocardiographic assessment of coronary flow reserve.

Clinical implications of exercise-induced regional wall motion abnormalities in significant aortic regurgitation

BACKGROUND

Significant aortic regurgitation (AR) is sometimes accompanied by regional wall motion abnormalities (RWMA) during exercise stress echocardiography. The aim of this study was to estimate the association between RWMA after exercise and in the presence of significant AR in patients with coronary artery disease (CAD) or volume overload and to predict the eventual need for aortic valve replacement (AVR).

METHODS AND RESULTS

We retrospectively reviewed 182 patients with significant AR who underwent exercise echocardiography. In addition, we investigated patients with AR who underwent coronary angiography (CAG) or coronary computed tomography angiography (CCTA) and were diagnosed with CAD. The presence of RWMA after exercise was defined as newly developed RWMA after exercise and included all changes in wall motion. Patients were divided into two groups according to the presence of RWMA after exercise: the RWMA group (n = 42) and non-RWMA group (n = 140). In the RWMA group, 31 patients (73.8%) underwent coronary artery evaluation by CAG or CCTA. Only two patients in the RWMA group were diagnosed with current CAD and underwent percutaneous coronary intervention. Patients with RWMA were older (61.6 ± 10.8 vs 52.0 ± 13.7 years, P < .001), had more severe AR (54.8% vs 32.9%), and underwent AVR more frequently (40.5% vs 14.3%, P = .001) than patients without RWMA. METs (odds ratio [OR], 0.796; P = .019), difference between rest and postexercise left ventricular end-diastolic volume (OR, 0.967; P = .001), and the difference between pre- and postexercise left ventricular end-systolic volume (OR, 1.113; P < .001) were identified as independent factors associated with RWMA after exercise according to multivariable logistic regression analysis. The majority of wall motion changes were seen in the lateral and inferior segments, and the locations of wall motion changes were relatively consistent with the direction of the AR jet. The relationship between RWMA after exercise and time to AVR was investigated by simple linear regression (hazard ratio [HR], 3.402; P < .001). After adjusting for baseline parameters of diastolic blood pressure, left ventricular end-systolic dimension (LVESD), aorta size, deceleration time, and METs, the presence of RWMA after exercise was not predictive of time to AVR (HR, 1.106; P = .81). On the other hand, without forcible entry of RWMA after exercise, LVESD (HR, 1.119; P < .001) and METs (HR, 0.828; P = .006) independently predicted the eventual need for AVR as an outcome.

CONCLUSION

The degree of change in wall motion from rest to exercise in those with significant AR was not correlated with CAD, but was correlated with the severity of volume overload and exercise-induced preload changes, as well as the direction of the AR jet. In addition, RWMA after exercise had no role in predicting the need for AVR.

Comparison of Instantaneous Wave-Free Ratio (iFR) and Fractional Flow Reserve (FFR) with respect to Their Sensitivities to Cardiovascular Factors: A Computational Model-Based Study

While coronary revascularization strategies guided by instantaneous wave-free ratio (iFR) are, in general, noninferior to those guided by fractional flow reserve (FFR) with respect to the rate of major adverse cardiac events at one-year follow-up in patients with stable angina or an acute coronary syndrome, the overall accuracy of diagnosis with iFR in large patient cohorts is about 80% compared with the diagnosis with FFR. So far, it remains incompletely understood what factors contribute to the discordant diagnosis between iFR and FFR. In this study, a computational method was used to systemically investigate the respective effects of various cardiovascular factors on FFR and iFR. The results showed that deterioration in aortic valve disease (e.g., regurgitation or stenosis) led to a marked decrease in iFR and a mild increase in FFR given fixed severity of coronary artery stenosis and that increasing coronary microvascular resistance caused a considerable increase in both iFR and FFR, but the degree of increase in iFR was lower than that in FFR. These findings suggest that there is a high probability of discordant diagnosis between iFR and FFR in patients with severe aortic valve disease or coronary microcirculation dysfunction.

Transcatheter Versus Surgical Aortic Valve Replacement in Patients With Prior Cardiac Surgery in the Randomized PARTNER 2A Trial

OBJECTIVES

The aim of this study was to further evaluate clinical outcomes in patients with and without PCS.

BACKGROUND

Prior cardiac surgery (PCS) is associated with increased surgical risk and post-operative complications following surgical aortic valve replacement (SAVR), but whether this risk is similar in transcatheter aortic valve replacement (TAVR) is unclear.

METHODS

In the PARTNER 2A (Placement of Aortic Transcatheter Valve) trial, 2,032 patients with severe aortic stenosis at intermediate surgical risk were randomized to TAVR with the SAPIEN XT valve or SAVR. Adverse clinical outcomes at 30 days and 2 years were compared using Kaplan-Meier event rates and multivariate Cox proportional hazards regression models. The primary endpoint of the PARTNER 2 trial was all-cause death and disabling stroke.

RESULTS

Five hundred nine patients (25.1%) had PCS, mostly (98.2%) coronary artery bypass grafting. There were no significant differences between TAVR and SAVR in patients with or without PCS in the rates of the primary endpoint at 30 days or 2 years. Nevertheless, an interaction was observed between PCS and treatment arm; whereas no-PCS patients treated with TAVR had higher rates of 30-day major vascular complications than patients treated with SAVR (adjusted hazard ratio: 2.66; 95% confidence interval: 1.68 to 4.22), the opposite was true for patients with PCS (adjusted hazard ratio: 0.27; 95% confidence interval: 0.11 to 0.66) (p_interaction <0.0001). A similar interaction was observed for life-threatening or disabling bleeding.

CONCLUSIONS

In the PARTNER 2A trial of intermediate-risk patients with severe aortic stenosis undergoing SAVR versus TAVR, the relative risk for 2-year adverse clinical outcomes was similar between TAVR and SAVR in patients with or without PCS.

Coronary flow reserve in mitral stenosis before and after percutaneous balloon mitral valvuloplasty

We aimed to evaluate the coronary flow reserve (CFR) before and after percutaneous balloon mitral valvuloplasty (PBMV) in patients with mitral stenosis (MS) and its association to clinical events. A prospective study included 45 patients with mitral stenosis candidate for PBMV (age 38 ± 19 years, 27 were females) and 20 with matched age and sex, healthy controls were included in the study. Noninvasive CFR was measured using transthoracic echocardiography and utilizing adenosine stress echocardiography (0.14 mg/kg/min) before PMBV, and one weak post PBMV using multi-tract balloon valvuloplasty technique. CFR was significantly lower in patients with MS compared to controls (P < 0.001). Moreover the CFR was significantly increased post-PBMV (P < 0.001) associated with significant increase in LVEF% (P < 0.05), decrease in systolic pulmonary artery pressure (P < 0.001), significant increase in TAPSE (P < 0.001). CFR was significantly correlated with the degree of change (Δ) in MVA, TAPSE, LVEF%, mean mitral PG and sPAP (r = 0.77, P < 0.001, r = 0.63; P < 0.001; r = 0.42; P < 0.05; r = -0.81; P < 0.001 and r = -0.65; P < 0.001). Mitral valve stenosis was associated with significantly impaired coronary flow reserve that significantly improved after PMBV. The improved CFR values were significantly correlated with the gain in the MVA and the improvement in the functions of both left and right ventricles.

Differences in Aortic Valve and Left Ventricular Parameters Related to the Severity of Myocardial Fibrosis in Patients with Severe Aortic Valve Stenosis

Objective

This study investigated the morphological and functional characteristics of the aortic valve and the left ventricular (LV) systolic functional parameters and myocardial mass related to the severity of myocardial fibrosis (MF) in patients with severe aortic valve stenosis (AS).

Materials and Methods

We retrospectively enrolled 81 patients (48 men; mean age: 59±12 years) with severe AS who underwent transthoracic echocardiography (TTE), cardiac computed tomography (CCT), and cardiovascular magnetic resonance (CMR) within 1 month and subsequent aortic valve surgery. Degree of MF was determined on delayed contrast-enhanced CMR with visual sub-segmental analysis-based quantification and was classified into three groups (no, mild, and severe) for identifying the differences in LV function and characteristics of the aortic valve. One-way ANOVA, Chi-square test or Fisher’s exact test were used to compare variables of the three groups. Univariate multinomial logistic regression analysis was performed to determine the association between the severity of MF and variables on imaging modalities.

Results

Of 81 patients, 34 (42%) had MF (mild, n = 18; severe, n = 16). Aortic valve calcium volume score on CCT, aortic valve area, LV mass index, LV end-diastolic volume index on CMR, presence of mild aortic regurgitation (AR), transaortic mean pressure gradient, and peak velocity on TTE were significantly different among the three groups and were associated with severity of MF on a univariate multinomial logistic regression analysis. Aortic valve calcium grade was different (p = 0.008) among the three groups but not associated with severity of MF (p = 0.375).

Conclusions

A multi-imaging approach shows that severe AS with MF is significantly associated with more severe calcific AS, higher LV end-diastolic volume, higher LV mass, and higher prevalence of mild AR.

Characterization of coronary flow reserve and left ventricular remodeling in a mouse model of chronic aortic regurgitation with carvedilol intervention

OBJECTIVES

We hypothesized that left ventricular (LV) remodeling might be exaggerated by an impaired coronary flow reserve in mice with chronic severe aortic regurgitation, and carvedilol, a β-adrenoceptor blocker, could regress the course.

METHODS

Severe aortic regurgitation was induced by retrograde puncture of the aortic valve leaflets under sonographic guidance in 12-week-old male C57BL/6J mice. Four weeks after regurgitation, the mice were treated with carvedilol (30 mg/kg/d) or not treated (control). Before and 4 weeks after carvedilol treatment, the coronary flow reserve and LV structure and function were evaluated by echocardiography. Cardiomyocytes and fibrosis were validated by histologic analysis.

RESULTS

Four-week aortic regurgitation caused a decreased LV ejection fraction and an increased LV end-systolic volume index. Regurgitation also impaired the coronary flow reserve due to an increase in the basal coronary peak diastolic velocity and velocity-time integral combined with the absence of substantial changes in the hyperemic coronary peak diastolic velocity and velocity-time integral. Four more weeks of regurgitation further deteriorated LV remodeling and coronary perfusion in the control group. In contrast, the carvedilol-treated group showed attenuated LV remodeling and a higher coronary flow reserve by decreasing the basal peak diastolic velocity and velocity-time integral without substantial changes in the hyperemic peak diastolic velocity and velocity-time integral. The coronary flow reserve and its pretreatment versus posttreatment difference were positively correlated with the pretreatment versus posttreatment LV ejection fraction and end-systolic volume index differences. In the carvedilol-treated group, subendocardial fibrosis was significantly reduced (P < .05), and the cardiomyocyte cross-sectional area tended to be smaller.

CONCLUSIONS

In mice with chronic severe aortic regurgitation, carvedilol therapy significantly improves the impaired coronary flow reserve and sufficiently attenuates adverse LV remodeling. Sustained coronary flow reserve impairment indicates progressive LV remodeling.

Differences in coronary blood flow in aortic regurgitation and systemic arterial hypertension have implications for diastolic blood pressure targets: a systematic review and meta-analysis

The objective was to evaluate coronary blood flow (CBF) in patients with systemic arterial hypertension (HTN) and to compare it with CBF in patients with aortic regurgitation (AR). A systematic literature search was conducted using the reference terms "coronary blood flow" and either "aortic regurgitation" or "hypertension." The selection criteria included CBF measurement in a concomitant control group, except studies evaluating CBF with aortic-valve replacement surgery. Twenty-two studies met the inclusion criteria. There were 318 persons with HTN, with 185 controls; and 102 persons with AR, with 144 controls. Despite an overall increase in CBF in HTN, CBF per gram of left ventricular mass was significantly (P < 0.0001) reduced. In contrast, CBF per gram of left ventricular mass was significantly (P = 0.004) increased in AR. Aortic regurgitation was associated with a significant (P < 0.0001) increase in CBF during systole and away from diastole, in contrast to persons with HTN. Aortic-valve replacement reversed the increase in systolic CBF. These data suggest that patients with HTN are more vulnerable than patients with AR to lower diastolic blood pressure (DBP), because resting CBF is compromised in HTN. Furthermore, patients with HTN may not compensate for DBP reductions by shifting CBF to systole, such as can occur with the low DBP in AR. Lower DBP in patients with AR cannot be used to justify treating patients with HTN to similar DBP because of the dramatic differences in CBF between the 2 conditions.

Aortic regurgitation and coronary microfistulae: double jeopardy causing myonecrosis

We describe a 3-case series of patients with a rare combination of mild-to-moderate aortic regurgitation and coronary microfistulae but nonobstructed epicardial coronary arteries who presented with symptoms of unstable angina and had confirmed myonecrosis. A plausible pathophysiological mechanism for this phenomenon and its clinical implication are discussed.

Selection of prosthetic heart valves

Cardiovascular surgery for the repair or replacement of diseased heart valves has continually improved since its introduction in the early 1960s. Despite advances in prosthetic heart valve design, to date there is no valve that is comparable to the native human valve with respect to durability, risk of thrombosis, and overall hemodynamic function. Although bioprosthetic devices are similar to the native valve with respect to thrombogenicity, durability is a significant concern, particularly in younger patients. Approximately 45% of implanted bioprosthetic valves fail at 10 years. In contrast, mechanical prostheses have a significantly lower incidence of structural failure, with an implantation life of greater than 20 years, and are thus more often used for patients under the age of 65. Unfortunately, significant hemodynamic and thrombotic issues have yet to be resolved with the latest generation of mechanical valves. Thus, careful analysis of patient factors and valve-related complications must be considered when treatment of heart valve disease is offered to the patient. The purpose of this review is to discuss the current recommendations for surgical intervention for heart valve disease.

Beta-blockers and coronary flow reserve: the importance of a vasodilatory action

Coronary flow reserve (CFR) is the maximal increase in coronary blood flow (CBF) above its resting level for a given perfusion pressure when coronary vasculature is maximally dilated. Normally, hyperaemic CBF reaches values at least 2- to 3-fold greater than resting CBF. Reduction of CFR is mainly due to epicardial coronary artery stenosis or to coronary microvascular dysfunction. CFR can be determined by several techniques that measure CBF itself (e.g. positron emission tomography) or CBF velocities (Doppler methods) from which coronary flow velocity reserve is calculated. Hyperaemic coronary vasodilation can be obtained by pharmacological agents (e.g. adenosine and dipyridamole), but also by the cold pressure test. Long-term antihypertensive treatment induces significant improvement of CFR, which is parallel to the regression of left ventricular (LV) hypertrophy. First- and second-generation beta-adrenergic receptor antagonists (beta-blockers) have shown contradictory influences on CFR. This can be explained by the interaction of the effects on CBF at rest, generally reduced by these drugs, and after hyperaemia, when minimal coronary resistance appears to be either increased or reduced. Third-generation beta-blockers (e.g. carvedilol and nebivolol), which have vasodilating capacity, improve hyperaemic CBF. This occurs as a result of a reduction in minimal resistance, which can be attributed to alpha-adrenergic blockade and/or to a nitric oxide-mediated effect. This improvement is clearly beneficial in patients with coronary artery disease and indicates an improved coronary microvascular function. Changes of CFR due to vasodilating beta-blockers improve microvascular angina pectoris or silent ischaemia in patients without epicardial artery stenosis, and are also helpful in predicting the response or the further improvement of LV function to treatment.

Using transthoracic Doppler echocardiography to diagnose reduced coronary flow velocity reserve in the posterior descending coronary artery in children with elevated right ventricular pressure

BACKGROUND

Advances in transthoracic Doppler echocardiography enable noninvasive measurements of coronary flow velocity and coronary flow velocity reserve (CFVR) in the posterior descending coronary artery (PD).

METHODS AND RESULTS

To evaluate CFVR in the PD of children with elevated right ventricular (RV) pressure, 19 children with RV pressure overload and 13 age-matched controls with normal RV pressure were studied using transthoracic Doppler echocardiography. Average peak flow velocity (APV) was measured at rest and in hyperemic conditions (intravenous administration of adenosine of 0.16 mg.kg(-1).min(-1)). Compared with controls, the PD CFVR was significantly reduced in the patients with elevated RV pressure (1.87+/-0.42 vs 2.49+/-0.55, p<0.01) because their mean baseline APV was significantly greater (27+/-6 vs 19+/-4 cm/s, p<0.01), although hyperemic APV was not significantly different (49+/-10 vs 48+/-14 cm/s, p=NS).

CONCLUSIONS

PD CFVR is limited in patients with elevated RV pressure because of elevation of the baseline resting flow velocity.

The non-invasive documentation of coronary microcirculation impairment: role of transthoracic echocardiography

Transthoracic Doppler echocardiographic-derived coronary flow reserve is an useful hemodynamic index to assess dysfunction of coronary microcirculation. Isolated coronary microvascular abnormalities are overt by reduced coronary flow reserve despite normal epicardial coronary arteries. These abnormalities may occur in several diseases (arterial hypertension, diabetes mellitus, hypercholesterolemia, syndrome X, aortic valve disease, hypertrophic cardiomyopathy and idiopathic dilated cardiomyopathy). The prognostic role of impaired microvascular coronary flow reserve has been shown unfavourable especially in hypertrophic or idiopathic dilated cardiomyopathies. Coronary flow reserve reduction may be reversible, for instance after regression of left ventricular hypertrophy subsequent to valve replacement in patients with aortic stenosis, after anti-hypertensive treatment or using cholesterol lowering drugs. Coronary flow reserve may increase by 30% or more after pharmacological therapy and achieve normal level >3.0. In contrast to other non invasive tools as positron emission tomography, very expensive and associated with radiation exposure, transthoracic Doppler-derived coronary flow reserve is equally non invasive but cheaper, very accessible and prone to a reliable exploration of coronary microvascular territories, otherwise not detectable by invasive coronary angiography, able to visualize only large epicardial arteries.

Myocardial contrast echocardiography assessment of acute changes in collateral perfusion of contralateral coronary artery with coronary flow reserve after coronary angioplasty

BACKGROUND

Coronary flow velocity reserve (CFVR) is used to evaluate the severity of epicardial and intramyocardial coronary artery disease. Collateral flow to an adjacent compromised myocardial territory may influence the CFVR of a specific artery.

METHODS

To assess the impact of collateral flow on CFVR, we measured CFVR and assessed perfusion area (PA) with myocardial contrast echocardiography in the right coronary arteries of 18 patients with total/subtotal occlusion of the left anterior descending coronary artery before and after angioplasty. A total of 10 patients had well-developed collaterals emerging from the right coronary artery (group I) and 8 patients did not (group II). Using a Doppler-tipped guidewire, we measured CFVR, which is defined as the ratio of papaverine-induced hyperemic average peak velocity of coronary flow to baseline.

RESULTS

Before angioplasty of the left anterior descending coronary artery, CFVR was significantly reduced in group I compared with group II (2.35 +/- 0.47 vs 3.26 +/- 0.54, P < .01). Baseline average peak velocity in group I before angioplasty was significantly greater than that after angioplasty (23.7 +/- 11.6 vs 19.2 +/- 9.7 cm/s, P < .05). After angioplasty, CFVR immediately increased in group I to 3.46 +/- 0.54 ( P < .001). The increase in CFVR was well correlated with the decrement in PA after angioplasty (r = 0.883, P < .001).

CONCLUSION

The CFVR of an artery that supplies extensive collaterals is limited because of an elevation in the baseline resting flow velocity. This restriction in CFVR improves proportionally with decreases in PA that occurs after angioplasty of the ipsilateral coronary artery. These data suggest that PA, in addition to coronary artery structure, influences CFVR.

Valvular Heart Disease

Aortic regurgitation (AR) is characterized by diastolic reflux of blood from the aorta into the left ventricle (LV). Acute AR typically causes severe pulmonary edema and hypotension and is a surgical emergency. Chronic severe AR causes combined LV volume and pressure overload. It is accompanied by systolic hypertension and wide pulse pressure, which account for peripheral physical findings, such as bounding pulses. The afterload excess caused by systolic hypertension leads to progressive LV dilation and systolic dysfunction. The most important diagnostic test for AR is echocardiography. It provides the ability to determine the cause of AR and to assess the severity of AR and its effect on LV size, function, and hemodynamics. Many patients with chronic severe AR may remain clinically compensated for years with normal LV function and no symptoms. These patients do not require surgery but can be followed carefully for the onset of symptoms or LV dilation/dysfunction. Surgery should be considered before the LV ejection fraction falls below 55% or the LV end-diastolic dimension reaches 55 mm. Symptomatic patients should undergo surgery unless there are excessive comorbidities or other contraindications. The primary role of medical therapy with vasodilators is to delay the need for surgery in asymptomatic patients with normal LV function or to treat patients in whom surgery is not an option. The goal of vasodilator therapy is to achieve a significant decrease in systolic arterial pressure. Future therapies may focus on molecular mechanisms to prevent adverse LV remodeling and fibrosis.

Coronary flow velocity and coronary flow velocity reserve in children with ventricular septal defect

To assess coronary flow characteristics in congenital heart defect with left ventricular (LV) volume overload, we examined 24 children (mean 12.1 +/- 7.1 months) with ventricular septal defect. The pulmonary to systemic flow ratio ranged from 1.1 to 3.0. Control group consisted of 10 age-matched children who had a history of Kawasaki disease with angiographically normal coronary artery in the acute phase. LV end-diastolic volume and LV mass were measured by left ventriculogram. With Doppler flow guide wire (0.014-inch), average peak flow velocity (APV) in left anterior descending coronary artery was recorded at rest and during hyperemia (0.16 mg/kg/min adenosine infusion intravenously). Coronary flow velocity reserve (CFVR) was calculated as the ratio of hyperemic/baseline APV. Seven patients were also studied 5-7 months after surgery. Compared with control subjects, CFVR was significantly reduced in patients with LVvolume overload (1.78 +/- 0.24 vs. 2.66 +/- 0.42, p < .0001) because baseline APV was significantly greater (30 +/- 8 vs. 23 +/- 5 cm/sec, p = 0.0027). Significant correlations were observed between CFVR and Qp/Qs, baseline APV, LV end-diastolic volume, or LVmass. Stepwise regression analysis showed that baseline APV and Qp/Qs were important determinants of CFVR (CFVR = 2.64-0.202 [Qp/Qs]-0.015 [APV] r = 0.83, p < 0.0001). In 7 patients with LVvolume overload, CFVR improved significantly after surgery because of reduction of baseline APV. CFVR is limited in patients with LV volume overload because of the elevation of baseline resting APV. LAD flow pattern is dependent on LV volume overload level and its changes after surgery.

Effects of coil closure of patent ductus arteriosus on left anterior descending coronary artery blood flow using transthoracic Doppler echocardiography

Transthoracic Doppler echocardiography provides noninvasive measurements of coronary blood flow in the left anterior descending coronary artery (LAD). This method has the potential to show the effects of acute changes in loading conditions on blood flow. Coil closure of patent ductus arteriosus (PDA) is a model of acute changes in blood pressure and left ventricular (LV) preload that influences coronary blood flow. We applied this technique to assess the coronary blood flow changes for patients with PDA before and immediately after PDA coil closure. We examined 9 patients (1.8 +/- 1.1 years) with simple PDA and 8 age-matched healthy children. LV dimensions and LV mass were measured. Maximum peak flow velocity and flow volume in the LAD were measured. Pulmonary to systemic flow ratios (Qp/Qs) were obtained by cardiac catheterization. After PDA coil closure, LV end-diastolic dimension decreased, and systolic and diastolic blood pressures increased significantly. The maximum peak flow velocity, LAD flow volume, and the ratio of LAD flow volume to LV mass increased significantly. The changes in maximum peak flow velocity and the ratio of LAD flow volume to LV mass (F/M) correlated positively with the changes in diastolic pressure and Qp/Qs. In 5 patients who had Qp/Qs > 1.5, the mean F/M was significantly lower compared with control subjects, but they increased to normal values after coil closure of PDA. PDA coil closure increases diastolic pressure and decreases Qp/Qs, resulting in improvement of myocardial perfusion. These findings provide new insights into the relationship between cardiac function and coronary circulation in pediatric patients with heart diseases associated with PDA.

Approach to the patient with chest pain and nonobstructive coronary artery disease

Patients with chest pain and nonobstructive coronary artery disease (NOCAD) utilize a significant part of our health care resources. Their diagnosis and treatment can often be difficult and time consuming. A simple classification system and stepwise diagnostic approach may help to reduce unnecessary testing. Also, utilization of a chest pain clinic may be beneficial for these patients.

Evaluation by Contrast-Enhanced Electron Beam Computed Tomography of Myocardial Perfusion and Tissue Characteristics in Congenital Aortic Stenosis

The evaluation of myocardial perfusion and tissue characteristics gives useful information regarding the indication for surgery. In the present study, two-phase contrast enhanced electron beam computed tomography (EBT) was used to quantitatively examine myocardial perfusion and the tissue characteristics of the left ventricular (LV) myocardium in congenital aortic stenosis (AS). The AS group comprised 15 patients and the control group had 14 non-AS patients. Myocardial ischemia and tissue characteristics were evaluated by the ratio of the incremental CT number of the myocardium (M) and the lumen (L) of the LV (M/L) in, the early phase with and without dipyridamole (Dp) loading and in the late phase after enhancement (respectively). In a comparison between the AS group and the controls, mean early M/Ls were significantly lower in the AS group than in the controls (20+/-5% vs 37+/-10%, p<0.01) and mean late M/Ls in the AS group were also significantly lower (47+/-11% vs 62+/-13%, p<0.01). In the AS patients, early M/Ls in the subendocardial and apical regions were especially lower than those of other segments, but the late M/Ls in these segments were inversely higher than those of other segments. These results suggest 2 things: (1) the existence of latent LV myocardial ischemia in AS patients, which is probably because of a hypertrophied LV wall, in turn caused by afterload, and (2) the presence of more myocardial ischemia and interstitial fibrosis in the subendocardial and apical regions of the AS heart. Using Dp loading for the AS patients increased the clarity of the contrast images. Contrast-enhanced EBT is useful for evaluating myocardial characteristics and perfusion in AS, and gives new insight into the LV wall characteristics in AS, as well as an indication for surgical correction of congenital AS.

Blood flow in the left anterior descending coronary artery in children with ventricular septal defect

High-frequency echocardiography offers a noninvasive approach for imaging left anterior descending coronary artery (LAD) blood flow from a transthoracic window. The purpose of this study was to assess the effects of left ventricular (LV) volume overload on LAD flow in pediatric patients with ventricular septal defect (VSD). The study subjects consisted of 38 children with VSD and 15 healthy children. LV mass, LAD diameter, and LAD flow were measured by using transthoracic echocardiography, then LAD diameter and LV mass were indexed for body surface area. Pulmonary to systemic flow ratios (Qp/Qs) were obtained by cardiac catheterization. The Qp/Qs ratios ranged from 1.2 to 3.1 (mean 2.1 +/- 0.5). The mean LAD flow velocities, flow velocity integrals, and flow volumes were significantly higher in the patients than in the control subjects. LAD flow velocity and flow volume showed significant positive correlations with Qp/Qs, LV mass, and LV end-diastolic volume. Stepwise regression analysis revealed that Qp/Qs was the most important determinant of both LAD flow velocity (r(2) = 0.45, P < .0001) and LAD flow volume (r(2) = 0.44, P < .0001). The ratios of LAD flow volume to LV mass did not differ between the 2 groups. In 8 patients who underwent surgical treatment, LAD flow velocity, flow velocity integral, and flow volume decreased significantly after surgery. The current results suggest that patients with VSD have a higher resting coronary blood flow, and that LAD flow pattern is dependent on LV volume overload and changes after surgery.

Coronary flow reserve improves after aortic valve replacement for aortic stenosis: an adenosine transthoracic echocardiography study

OBJECTIVES

The goal of this study was to assess coronary flow reserve (CFR) before and after aortic valve replacement (AVR).

BACKGROUND

Coronary flow reserve is impaired under conditions of left ventricular (LV) hypertrophy. It is not known whether CFR improves with regression of LV hypertrophy in humans.

METHODS

We investigated 35 patients with pure aortic stenosis, LV hypertrophy and normal coronary arteriograms. Patients underwent adenosine transthoracic echocardiography on two occasions--immediately before AVR and six months postoperatively. Left ventricular mass, distal left anterior descending coronary artery (LAD) diameter, flow and CFR were assessed on each occasion.

RESULTS

Distal LAD diameter was successfully imaged in 30 patients (86%), and blood flow was successfully imaged in 27 (77%). Paired data were subsequently available in 24 patients, of whom 14 were men, mean age 68.1+/-12.5 years, body mass index 24.5+/-2.0 kg/m2, aortic valve gradient 93+/-32 mm Hg. Pre- to post-AVR a significant decrease was seen in LV mass (271+/-38 vs. 236+/-32g, p<0.01) and LV mass index (154+/-21 vs. 134+/-21 g/m2, p< 0.01). Distal LAD diameter fell from 2.27+/-0.37 to 2.23+/-0.35 mm, p = 0.08). Pre- to post-AVR there was no significant change in resting parameters of peak diastolic velocity (0.43+/-0.16 vs. 0.41+/-0.11 m/s), distal LAD flow 23.3+/-10.1 vs. 20.9+/-5.2 ml/min or distal LAD flow scaled for LV mass (8.7+/-3.8 vs. 9.0+/-2.5 ml/min/100 g LV mass), but there was significant increase in hyperemic peak diastolic velocity (0.71+/-0.26 vs. 1.08+/-0.24 m/s; p<0.01), distal LAD flow (37.8+/-11.3 vs. 53.5+/-16.1 ml/min; p<0.01) and distal LAD flow scaled for LV mass (14.3+/-5.0 vs. 23.3+/-8.5 ml/min/100 g LV mass; p<0.01). Coronary flow reserve, therefore, increased from 1.76+/-0.5 to 2.61+/-0.7.

CONCLUSIONS

Coronary flow reserve increases after AVR for aortic stenosis. This increase occurs in tandem with regression of LV hypertrophy.

Coronary flow reserve is supranormal in endurance athletes: an adenosine transthoracic echocardiographic study

OBJECTIVE

To compare coronary flow reserve in endurance athletes and healthy sedentary controls, using adenosine transthoracic echocardiography.

METHODS

29 male endurance athletes (mean (SD) age 27.3 (6.6) years, body mass index (BMI) 22.1 (1.9) kg/m(2)) and 23 male controls (age 27.2 (6.1) years, BMI 23.9 (2.6) kg/m(2)) with no coronary risk factors underwent transthoracic echocardiographic assessment of distal left anterior descending coronary artery (LAD) diameter and flow, both at rest and during intravenous adenosine infusion (140 microg/kg/min).

RESULTS

Distal LAD diameter and flow were adequately assessed in 19 controls (83%) and 26 athletes (90%). Distal LAD diameter in athletes (2.04 (0.25) mm) was not significantly greater than in sedentary controls (1.97 (0.27) mm). Per cent increase in LAD diameter following 400 microg sublingual nitrate was greater in the athletes than in the controls, at 14.1 (7. 2)% v 8.8 (5.7)% (p < 0.01). Left ventricular mass index in athletes exceeded that of controls, at 130 (19) v 98 (14) g/m(2) (p < 0.01). Resting flow among the athletes (10.6 (3.1) ml/min; 4.4 (1.2) ml/min/100 g left ventricular mass) was less than in the controls (14.3 (3.6) ml/min; 8.2 (2.2) ml/min/100 g left ventricular mass) (both p < 0.01). Hyperaemic flow among the athletes (61.9 (17.8) ml/min) exceeded that of the controls (51.1 (14.6) ml/min; p = 0.02), but not when corrected for left ventricular mass (25.9 (5.6) v 28.5 (7.4) ml/min/100 g left ventricular mass; NS). Coronary flow reserve was therefore substantially greater in the athletes than in the controls, at 5.9 (1.0) v 3.7 (0.7) (p < 0.01).

CONCLUSIONS

Coronary flow reserve in endurance athletes is supranormal and endothelium independent vasodilatation is enhanced. Myocardial hypertrophy per se does not necessarily impair coronary flow reserve. Adenosine transthoracic echocardiography is a promising technique for the investigation of coronary flow reserve.

Aortic regurgitation reduces the accuracy of exercise echocardiography for diagnosis of coronary artery disease

The association of aortic regurgitation with left ventricular size, hypertrophy, and abnormal coronary flow may influence the accuracy of stress testing techniques for the diagnosis of coronary disease. We examined the diagnostic accuracy of treadmill exercise echocardiography to predict coronary artery disease in 76 patients with moderate to severe aortic regurgitation. Rest and poststress images were interpreted by 2 experienced observers, and accuracy was defined by comparison with stenoses >/=50% diameter at coronary angiography. Results were compared with accuracy in a control group of previously published studies in patients without valvular heart disease. After 6 patients were excluded because of a submaximal heart rate response (<85% age-predicted maximal heart rate), 70 patients were included in the final analysis. Patients with aortic regurgitation were of comparable age to the control group and exercised to similar workload. In 16 (23%) patients with significant coronary artery disease and significant aortic regurgitation, the sensitivity of exercise echocardiography was 56% compared with 83% in the control group (P =.03). The specificity in 54 patients with aortic regurgitation but no significant coronary artery disease was 67% compared with 83% in the control group (P =.02). Accuracy was 64% in aortic regurgitation compared with 83% in the control group (P =.02). In patients with aortic regurgitation, accuracy in the left anterior descending artery territory (76%) marginally exceeded that in the posterior (right + circumflex coronary artery) circulation (70%). Thus the presence of significant aortic regurgitation affects the regional wall motion of the left ventricle during exercise and adversely affects the accuracy of exercise echocardiography for the diagnosis of coronary artery disease.

Restricted coronary flow reserve in patients with mitral regurgitation improves after mitral reconstructive surgery

OBJECTIVES

The purpose of this study was to assess coronary flow characteristics in patients with chronic mitral regurgitation (MR).

BACKGROUND

Coronary flow reserve (CFR) has been reported to be restricted in cases with left ventricular (LV) volume overload caused by aortic regurgitation and increased LV preload.

METHODS

The study populations consisted of 31 patients with nonrheumatic chronic MR. Eleven with chest pain and normal coronary arteries served as control subjects. Phasic coronary flow velocities were obtained in the proximal segment of the angiographically normal left anterior descending coronary artery at rest and during hyperemia (0.14 mg/kg/min adenosine infusion intravenously) using a 0.014-in. (0.036 cm), 15-MHz Doppler guide wire. Coronary flow reserve was obtained from the ratio of hyperemic/baseline time-averaged peak velocity (APV). Thirteen cases who underwent mitral valve reconstructive surgery were also studied 1 month after surgery.

RESULTS

Compared with control subjects, CFR was significantly reduced in cases with MR (2.1+/-0.5 vs. 33+/-0.6, respectively, p < 0.01) because baseline APV was significantly greater (28+/-8 vs. 19+/-6 cm/s, respectively, p < 0.01), although maximal hyperemic APV was not significantly different (56+/-14 vs. 61+/-16 cm/s, respectively, p = NS). Significant correlations were obtained between CFR and LV end-diastolic pressure (LVEDP) (r = 0.70, p < 0.01), LV mass index (r = 0.42, p < 0.01), LV end-diastolic volume (r = 038, p = 0.04) and MR volume (r = 0.39, p = 0.03), and stepwise regression analysis showed LVEDP was the most important determinant of CFR in MR (r2 = 0.49, p < 0.0001). This restricted CFR improved significantly after mitral valve reconstructive surgery (2.1+/-0.5 vs. 3.1+/-0.6, respectively, p < 0.01) because of reduction of baseline APV (28+/-8 vs. 21+/-8 cm/s, respectively, p < 0.01).

CONCLUSIONS

Coronary flow reserve is limited in cases with MR because of elevation of baseline resting flow velocity. This reduction of CFR correlates well with increase in LV preload, mass and volume overload, especially with increase in LV preload, and this restricted CFR improves after mitral valve surgery.

Chronic aortic regurgitation. Role of medical therapy and optimal timing for surgery

Aortic valve replacement should be performed once significant symptoms develop. Lacking important symptoms, operation should also be performed in patients with aortic regurgitation who manifest consistent and reproducible evidence of either LV contractile dysfunction at rest or extreme LV dilation. Noninvasive imaging techniques should play a major role in this evaluation. An important clinical decision, such as recommending aortic valve replacement in the asymptomatic patient, should not be based on a single echocardiographic or radionuclide angiographic measurement alone. When these data consistently indicate impaired contractile function at rest or extreme LV dilation on repeat measurements, however, operation is indicated in the asymptomatic patient. This strategy should reduce the likelihood of irreversible LV dysfunction in these patients and enhance long-term postoperative survival.

Angina pectoris in patients with aortic stenosis and normal coronary arteries. Mechanisms and pathophysiological concepts

BACKGROUND

The incidence of angina pectoris (AP) in patients with severe aortic stenosis (AS) and normal coronary arteries has been reported to be 30% to 40%. The exact pathophysiological mechanism, however, is not known. The purpose of this work was to evaluate the various hemodynamic and angiographic determinants of myocardial perfusion in 61 patients with severe AS.

METHODS AND RESULTS

In a retrospective analysis, 61 patients with severe AS and without significant coronary artery disease were studied. Thirty-three patients with atypical chest pain and angiographically normal arteries served as control subjects. Patients were divided into two groups: 32 with AP and 29 without AP. Quantitative coronary angiography was performed in 59 patients and 22 control subjects. Coronary flow reserve was determined in 29 patients and 7 control subjects by use of coronary sinus thermodilution technique. Patients with AP had a lower left ventricular (LV) muscle mass, an increased LV peak systolic pressure, and increased wall stress than those without AP. Vessels of the left coronary artery were smaller and coronary flow reserve was lower in patients with AP than in those without. Inadequate L V hypertrophy with an increased wall stress was found in patients with AP but not in patients without AP.

CONCLUSIONS

Myocardial ischemia in patients with severe AS can occur in the absence of coronary artery disease and appears to be due to inadequate LV hypertrophy with high systolic and diastolic wall stresses and a reduced coronary flow reserve. The cause of inadequate LV hypertrophy, however, remains unclear.

Transesophageal Doppler echocardiographic assessment of systolic and diastolic coronary blood flow velocities at baseline and during adenosine triphosphate-induced coronary vasodilation in chronic aortic regurgitation

Few reports exist on the changes in systolic and diastolic coronary flow velocities (CFVs) at baseline and during coronary vasodilation in patients with chronic aortic regurgitation (AR). We examined the left anterior descending CFVs in 21 patients with AR (11 patients with mild AR and 10 patients with moderate to severe AR), 9 patients without AR (no AR group), and 6 patients who had undergone surgery for moderate to severe AR (postoperation group) with transesophageal Doppler echocardiography. Adenosine triphosphate (ATP) was infused into a peripheral right arm vein at four different doses (35, 70, 100, and 140 micrograms/kg/min). Coronary flow velocity response in systole and diastole was calculated as the ratio of systolic peak and mean and diastolic peak and mean CFVs during maximal ATP infusion to those at baseline. The systolic peak and mean CFVs and the diastolic peak and mean CFVs at baseline were significantly increased in the moderate to severe group compared with those in the other groups (p < 0.05, respectively). Systolic and diastolic CFVs were significantly increased during ATP infusions in the four groups. No significant differences of systolic and diastolic CFVs were observed among the four groups during maximal ATP infusion. The coronary flow velocity response calculated from the peak and mean diastolic CFVs were significantly decreased in the moderate to severe group (1.6 +/- 0.3 and 1.7 +/- 0.4) compared with those in the other three groups (3.6 +/- 0.7 and 3.2 +/- 1.1 in the no AR group, 2.6 +/- 0.6 and 2.5 +/- 0.4 in the mild group, and 2.5 +/- 0.7 and 2.4 +/- 0.6 in the postoperation group) (p < 0.05, respectively). In conclusion, the systolic and diastolic left CFVs at baseline appeared to be significantly increased in patients with moderate to severe chronic AR. However, the velocities during coronary vasodilation by ATP were equal to those in other groups, resulting in a decrease of coronary flow velocity response in systole and diastole.

Transesophageal assessment of coronary flow velocity reserve during "regular" and "high"-dose dipyridamole stress testing

To assess the effect of regular and high-dose dipyridamole on coronary flow velocity in the left anterior descending artery (LAD), and to determine whether assessment of coronary flow velocity reserve (CFVR) is more sensitive for detection of ischemia than standard echocardiographic criteria, 47 patients were studied prospectively: 16 patients with stenosis of the LAD, 18 patients with angiographically normal LADs, and 13 patients with minimal disease. Patients underwent transesophageal echocardiographic study of wall motion and LAD flow velocity at baseline and at hyperemia, and for angina and electrocardiographic changes. The mean CFVR values after 0.56 mg/kg after 0.84 mg/kg of dipyridamole were similar: 2.52 +/- 0.87 versus 2.62 +/- 0.90. A CFVR <2.3 (normals mean -2 SDs) was more sensitive (88% at both doses) for the detection of underlying coronary obstruction than was wall motion monitoring (44% and 75%, respectively). The combination of CFVR <2.3 and wall monitoring was more sensitive than index alone (94% at both 0.56 and 0.84 mg/kg). The rate-pressure product was not significantly different at the two doses of dipyridamole. When flow response is the end point of stress testing, as with transesophageal monitoring, the 0.56 mg/kg dose of dipyrid mole is adequate, but when ischemia is the end point (as with wall motion monitoring by 2-dimensional echocardiography), the dose of 0.84 mg/kg is more sensitive.

Transesophageal Doppler echocardiographic assessment of left coronary blood flow velocity in chronic aortic regurgitation

Assessment of systolic and diastolic coronary blood flow velocities (FVs) in patients with aortic regurgitation (AR) has remained a clinical challenge. We recorded left anterior descending coronary blood FV in 21 patients with chronic AR an in 6 control subjects using transesophageal pulsed Doppler echocardiography. In 7 patients FV was measured 4.0 +/- 5.2 months after aortic valve replacement. Peak and mean FVs during systole and diastole and systolic/diastolic ratios of these FVs were determined. Left ventricular (LV) mass index was calculated by means of standard M-mode echocardiography. In patients with severe AR, peak and mean systolic FVs were significantly increased (34 +/- 8 cm/sec and 21 +/- 6 cm/sec, respectively) compared with FVs in the control group (15 +/- 4 and 12 +/- 3 cm/sec, respectively) and in patients with mild AR (17 +/- 3 cm/sec and 13 +/- 2 cm/sec, respectively). Peak and mean systolic FVs were also significantly increased in severe AR (54 +/- 13 cm/sec and 33 +/- 9 cm/sec, respectively) compared with FVs in the control (30 +/- 8 cm/sec and 21 +/- 5 cm/sec, respectively) and mild AR groups (30 +/- 5 cm/sec and 21 +/- 4 cm/sec, respectively). Peak systolic and diastolic FVs were correlated significantly with LV mass index (r = 0.72 and r = 0.73, respectively). Systolic and diastolic FVs and LV mass index were significantly decreased, normalized or both after aortic valve surgery. In conclusion, LV mass seems to have an effect on the significantly increased systolic and diastolic left coronary blood FV pattern in patients with chronic, severe AR. Increased systolic and diastolic FV appears to be normalized in the late period after surgery.

Epicardial coronary arteries are not adequately sized in hypertensive patients

OBJECTIVES

This study sought to compare coronary artery dimensions in hypertensive patients and normal subjects.

BACKGROUND

Myocardial oxygen demand at rest and corresponding coronary blood flow are the main determinants of large coronary artery dimensions in humans. Coronary diameters are increased in aortic valve disease.

METHODS

Left main, proximal and distal left anterior descending and proximal circumflex coronary artery diameters were measured by quantitative angiography in 10 control subjects (group 1) and 26 untreated hypertensive patients, 12 without (group 2a) and 14 with (group 2b) left ventricular hypertrophy. All patients had normal cholesterol levels and angiographically normal coronary arteries. Measurements were made at baseline and after 2 mg of intracoronary isosorbide dinitrate to obtain maximal dimensions of vessels. Coronary flow velocity was measured in the distal left anterior descending coronary artery by Doppler ultrasound.

RESULTS

Despite a higher rate-pressure product in hypertensive patients, all segment diameters were slightly but not significantly higher at baseline in group 2b than in groups 1 and 2a. Diameters were similar in the three groups after isosorbide dinitrate. Conversely, coronary flow velocity was significantly higher in hypertensive patients than in group 1 either at baseline (10.4 +/- 2.2 [mean +/- SD] cm/s [group 2a] and 12.8 +/- 2.4 cm/s [group 2b] vs. 6.5 +/- 2.0 cm/s [group 1], all p < 0.001) or after isosorbide dinitrate (6.8 +/- 2.8 cm/s [group 2a] and 7.8 +/- 2.1 cm/s [group 2b] vs. 3.7 +/- 0.8 cm/s [group 1], p < 0.01 and p < 0.001, respectively).

CONCLUSIONS

Despite an elevated myocardial oxygen demand, maximal dimensions of large coronary arteries are not increased in hypertensive patients, resulting in an elevated coronary flow velocity that may increase longitudinal shear stress at the endothelial surface. This elevated flow velocity might be an important determinant in the pathogenesis of atherosclerosis in hypertensive patients.

Reduced epicardial coronary vasodilator capacity in patients with left ventricular hypertrophy

BACKGROUND

Enlargement of the epicardial coronary arteries occurs in left ventricular (LV) hypertrophy as an adaptation to the increased coronary blood flow.

METHODS AND RESULTS

Vasodilator capacity of the epicardial coronary arteries was determined in 44 patients. The dose-response relation of intracoronary nitroglycerin was assessed in 14 patients (7 control subjects and 7 patients with aortic stenosis [study A]) using quantitative coronary angiography. In a second study (B), vasodilator capacity of the epicardial coronary arteries was determined in 15 control subjects and 15 patients with valvular heart disease. In study A, a curvilinear dose-response relation with maximal vasodilation after 90 micrograms intracoronary nitroglycerin was found in both control subjects and patients with aortic stenosis. Vasodilator capacity was reduced in those with aortic stenosis, although sensitivity to nitroglycerin was similar in both groups. In study B, coronary circumferential length at baseline was larger in those with LV hypertrophy (12.2 +/- 2.2 mm) than in control subjects (8.6 +/- 1.5 mm; P < .001); after 100 micrograms intracoronary nitroglycerin, it increased to 12.9 +/- 2.2 mm (6 +/- 5%) in those with LV hypertrophy and to 10.3 +/- 1.5 mm (21 +/- 8%; P < .001) in control subjects. An inverse relation between baseline circumferential length and its percent increase after nitroglycerin was found (r = -.71, P < .001).

CONCLUSIONS

Vasodilator capacity of the epicardial coronary arteries is reduced in patients with LV hypertrophy, although sensitivity to nitroglycerin is normal. This may be due to a flow-mediated decrease in coronary vasomotor tone and/or the occurrence of vascular remodeling with an enlargement of the coronary arteries.

Relation of phasic coronary flow velocity profile to clinical and hemodynamic characteristics of patients with aortic valve disease

BACKGROUND

Our objective was to assess phasic coronary blood flow and velocity characteristics of the proximal portion of the left anterior descending artery and to evaluate their relation to the clinical and hemodynamic manifestations in patients with aortic valve disease.

METHODS AND RESULTS

We examined 26 patients with chronic aortic regurgitation (AR), 12 patients with predominant aortic stenosis (AS), and 11 control subjects using an intravascular Doppler catheter with spectral analysis. Angiographic assessment of AR identified 10 patients with mild regurgitation and 16 with severe regurgitation. The resting systolic coronary flow velocity-time integral (VTI) was significantly higher and the diastolic VTI was slightly but significantly higher in patients with severe regurgitation than in those with mild regurgitation (11.8 +/- 4.2 vs 4.1 +/- 1.1 cm, P < .001; 18.5 +/- 5.8 vs 13.2 +/- 3.2 cm, P < .05) and control subjects (4.0 +/- 1.0 cm, P < .001 and 13.3 +/- 3.6 cm, P < .05), respectively. Patients with AS had a slightly lower resting systolic VTI (3.8 +/- 1.4 cm) and a higher diastolic VTI (14.6 +/- 3.7 cm) than control subjects. Resting coronary blood flow was greater in patients with aortic valve disease than in control subjects. There was a significant correlation between the ratio of the resting systolic to diastolic VTI (S/D ratio) and the ratio of the aortic systolic to diastolic pressure (r = .75, P < .001) in patients with AR. The S/D ratio was inversely correlated with left ventricular systolic pressure (r = -.92, P < .001) and positively correlated with the ratio of the aortic systolic to diastolic pressure (r = .68, P < .05) in patients with AS.

CONCLUSIONS

Our results indicate that hemodynamic changes related to aortic valve disease contribute to alterations in the resting phasic coronary blood flow and velocity profiles observed in these patients.

Abnormal nondefect zone myocardial thallium washout ratio in patients with reversible thallium defects and normal coronary arteriograms

Thallium myocardial defects in patients with no angiographic coronary artery stenosis have been attributed to attenuation effects and other artifacts. Of 323 patients having thallium myocardial imaging following dipyridamole infusion, 10 of 159 patients with a segmental perfusion abnormality were found to have no luminal diameter stenosis greater than 20% on coronary angiography and no electrocardiographic (ECG) evidence of myocardial infarction or left bundle branch block. A time-standardized regional thallium washout ratio was calculated as thallium myocardial counts with dipyridamole to counts without dipyridamole. In comparison to 10 age-matched control patients with no evidence of cardiac disease and no myocardial thallium defect, study patients had a lower regional myocardial thallium washout ratio from both the defect and nondefect (1.57 +/- 0.40 versus 2.27 +/- 0.92, p = 0.041) zones. Nine of the 10 study patients had independent evidence of noncoronary heart disease, including echocardiographic or ECG evidence of left ventricular hypertrophy in six patients. In patients with thallium defects and normal coronary arteriograms, a time-standardized regional thallium myocardial washout ratio for the nondefect zone may aid in the differentiation of patients with noncoronary heart disease from those with soft tissue artifacts.

Coronary arterial involvement in aortitis syndrome: Assessment by exercise thallium scintigraphy

It is important in patient management to evaluate coronary arterial involvement in aortitis syndrome. Twenty-one cases of aortitis syndrome who experienced chest pain were examined using exercise thallium scintigraphy. The patients were divided into 4 groups according to the angiographic findings. There were five patients with left main coronary arterial involvement (group A), four with left or right coronary arterial involvement (group B), nine with aortic regurgitation (group C), and three with pulmonary arterial involvement (group D). In groups A and B, all patients had positive ECGs and thallium perfusion defects. Group A patients showed extensive anterolateral perfusion defects, which were compatible with left main coronary arterial involvement. Groups C and D patients, who had normal coronary arteries, showed no remarkable perfusion defects although five had positive ECG findings. Thus, the sensitivity and specificity of exercise scintigraphy for detection of myocardial ischemia were 9/9 and 12/12, while those of stress ECG were 9/9 and 7/12 (58%), respectively. it is recommended that exercise thallium scintigraphy be used for detecting clinically occult but significant coronary arterial involvement in aortitis syndrome with chest pain.

Coronary flow reserve

The ability of the coronary circulation to autoregulate is essential for the heart to respond to metabolic demands. Several alterations in function may limit maximal coronary perfusion including atherosclerosis, structural abnormalities of small coronary vessels, extravascular compressive forces, thrombosis, abnormal endothelial regulatory function, and the effect of abnormal myocardium on the coronary circulation. Coronary flow reserve is a unifying concept that examines the limitation in myocardial perfusion that certain disease states impose. At present, even with state-of-the-art technology, the measurement of coronary flow reserve is difficult in routine clinical situations. As the ability to measure regional myocardial perfusion improves, coronary flow reserve may gain more widespread clinical use with perhaps as yet undiscovered therapeutic implications.