Anticoagulation Monitoring Part 2: Unfractionated Heparin and Low-Molecular-Weight Heparin

OBJECTIVE

To review the availability, mechanisms, limitations, and clinical application of point-of-care (POC) devices used in monitoring anticoagulation with unfractionated heparin (UFH) and low-molecular-weight heparins (LMWHs).

DATA SOURCES

Articles were identified through a MEDLINE search (1966–August 2004), device manufacturer Web sites, additional references listed in articles and Web sites, and abstracts from scientific meetings.

STUDY SELECTION AND DATA EXTRACTION

English-language literature from clinical trials was reviewed to evaluate the accuracy, reliability, and clinical application of POC monitoring devices.

DATA SYNTHESIS

The activated partial thromboplastin time (aPTT) and activated clotting time (ACT) are common tests for monitoring anticoagulation with UFH. Multiple devices are available for POC aPTT, ACT, and heparin concentration testing. The aPTT therapeutic range for UFH will vary depending upon the reagent and instrument employed. Although recommended by the American College of Chest Physicians Seventh Conference on Antithrombotic and Thrombolytic Therapy, establishing a heparin concentration–derived therapeutic range for UFH is rarely performed. Additional research evaluating anti-factor Xa monitoring of LMWHs using POC testing is necessary.

CONCLUSIONS

Multiple POC devices are available to monitor anticoagulation with UFH. For each test, there is some variability in results between devices and between reagents used in the same device. Despite these limitations, POC anticoagulation monitoring of UFH using aPTT and, more often, ACT is common in clinical practice, particularly when evaluating anticoagulation associated with interventional cardiology procedures and cardiopulmonary bypass surgery.

Acute hyperglycemia does not affect the reactivity of coronary microcirculation in humans

OBJECTIVE

There is some evidence that acute hyperglycemia (H) may cause vascular dysfunction in normal subjects. This study investigates whether acute, short-term H affects coronary vasodilatory function in healthy subjects.

DESIGN

Diastolic peak flow velocity in the left anterior descending coronary artery was measured at rest and after dipyridamole (0.56 mg/kg over 4 min) using transthoracic color Doppler echocardiography in 13 healthy men. Coronary flow reserve (CFR) was defined as the ratio of dipyridamole-induced coronary peak diastolic to resting peak diastolic flow velocity. CFR was measured both in euglycemia (E) and after 3 h H ( approximately 14 mmol/liter) by a variable infusion of glucose and octreotide (0.4 mg/h) to prevent increase in insulin concentration.

RESULTS

Fasting plasma glucose increased to 14.3 +/- 0.33 mmol/liter during the study and maintained variability within less than 10%. Plasma insulin remained nearly stable during H. Resting diastolic flow velocity was 18.5 +/- 0.6 cm/sec in E and increased to 20.0 +/- 0.7 cm/sec during H (P < 0.005). Dipyridamole infusion produced a marked increase in coronary flow velocity, which reached values of 50.8 +/- 2.9 cm/sec in E and 51.8 +/- 2.1 cm/sec in H (P = not significant). CFR was 2.78 +/- 0.16 in E and 2.59 +/- 0.12 in H (P = not significant).

CONCLUSION

Our study indicates that short-term hyperglycemia does not affect the vasodilatory response of coronary microcirculation in healthy subjects.

Direct demonstration by transthoracic Doppler echocardiography of adenosine-induced coronary steal in the collateral-dependent vessel

Coronary flow velocity reserve was measured to assess the frequency of coronary steal in the collateral-dependent coronary arteries using transthoracic Doppler echocardiography. Coronary steal occurred in half the vessels studied. There was no significant difference between coronary flow velocity reserve in poorly and well-developed collaterals.

Value of the myocardial performance index in myocardial infarction

The myocardial performance index represents an easy and reproducible parameter of both systolic and diastolic left ventricular function for the risk stratification of patients following acute myocardial infarction.

Coronary flow reserve in stress-echo lab. From pathophysiologic toy to diagnostic tool

The assessment of coronary flow reserve by transthoracic echocardiography has recently been introduced into clinical practice with gratifying results for the diagnosis of left anterior descending artery disease simultaneously reported by several independent laboratories. This technological novelty is changing the practice of stress echo for 3 main reasons. First, adding coronary flow reserve to regional wall motion allows us to have - in the same sitting - high specificity (regional wall motion) and a high sensitivity (coronary flow reserve) diagnostic marker, with an obvious improvement in overall diagnostic accuracy. Second, the technicalities of coronary flow reserve shift the balance of stress choice in favour of vasodilators, which are a more robust hyperemic stress and are substantially easier to perform with dual imaging than dobutamine or exercise. Third, the coronary flow reserve adds a quantitative support to the exquisitely qualitative assessment of wall motion analysis, thereby facilitating the communication of stress echo results to the cardiological world outside the echo lab. The next challenges involve the need to expand the exploration of coronary flow reserve to the right and circumflex coronary artery and to prove the additional prognostic value - if any - of coronary flow reserve over regional wall motion analysis, which remains the cornerstone of clinically-driven diagnosis in the stress echo lab.

Feasibility of Measuring Coronary Flow Velocity and Reserve in the Left Anterior Descending Coronary Artery by Transthoracic Doppler Echocardiography in a Relatively Obese American Population

BACKGROUND

Transthoracic Doppler echocardiography (TTDE) assessment of coronary flow velocity reserve (CFVR) has been validated in Asian and European centers. This methodology has not gained acceptability in the United States due to the bias that coronary flow velocity (CFV) by TTDE might be difficult in an obese population with relatively poor acoustic windows.

METHODS

Baseline CFV in the left anterior descending coronary artery (LAD) by TTDE was obtained in 67 nonselected American patients. A subset of 38/67 received adenosine infusion for measuring CFVR of the LAD.

PURPOSE

The aim of this study was twofold: (1) to determine the feasibility of measuring CFV and CFVR in the LAD by TTDE in a relatively obese American population, and (2) to compare CFV and CFVR values in this population with those previously obtained in a group of Japanese patients.

RESULTS

The mean body mass index (BMI) of the American population (28 +/- 6 kg/m2, range: 18-46 kg/m2) was significantly higher than that of the Japanese group (23 +/- 4 kg/m2, range: 15-37 kg/m2). Twenty-five American patients were classified as obese (BMI >30 kg/m2). Baseline CFV was obtained in 60/67 patients (feasibility: 90%) with a 10% need for intravenous contrast agent to enhance the delineation of the CFV envelope. The success rate in recording CFVR in American patients (92%) was nearly identical to that of a Japanese group (99%). The time-averaged peak diastolic coronary flow velocity increased from 15.6 +/- 5.5 cm/sec at baseline to 47.1 +/- 17.9 cm/sec during adenosine infusion, and CFVR was calculated to be 3.22 +/- 1.15 (range: 0.94-5.69). Intraobserver and interobserver variability for the CFV recording was 4.7 and 6.2%, respectively.

CONCLUSIONS

These results suggest that the noninvasive measurement of CFV and CFVR of the LAD is feasible even in a relatively obese American population. Furthermore, the success rates for recording CFV and CFVR are similar to those measured in a Japanese population. This methodology has the potential to provide useful physiological information on the coronary circulation in American patients.

Noninvasive assessment of coronary vasodilation using magnetic resonance angiography

OBJECTIVES

The purpose of this study was to investigate the use of coronary magnetic resonance angiography (MRA) for assessing human epicardial coronary artery vasodilation.

BACKGROUND

Coronary vasodilation plays a vital role in the human coronary circulation. Previous studies of epicardial coronary vasodilation have used invasive coronary angiography. Coronary MRA may provide an alternative noninvasive method to directly assess changes in coronary size.

METHODS

Thirty-two subjects were studied: 12 patients (age 55 +/- 18 years) and 20 healthy subjects (age 34 +/- 4 years). High-resolution multi-slice spiral coronary MRA (in-plane resolution of 0.52 to 0.75 mm) was performed before and after sublingual nitroglycerin (NTG). Quantitative analysis of coronary vasodilation was performed on cross-sectional images of the right coronary artery (RCA). A time-course analysis of coronary vasodilation was performed in a subset of eight subjects for 30 min after NTG. Signal-to-noise ratio was also measured on the in-plane RCA images.

RESULTS

Coronary MRA demonstrated a 23% increase in cross-sectional area after NTG (16.9 +/- 7.8 mm2 to 20.8 +/- 8.9 mm2, p <0.0001), with significant vasodilation between 3 and 15 min after NTG on time-course analysis. The MRA measurements had low interobserver variability (< or =5%) and good correlation with X-ray angiography (r=0.98). The magnitude of vasodilation correlated with baseline cross-sectional area (r=0.52, p=0.03) and age (r=0.40, p=0.019). Post-NTG images also demonstrated a 31% improvement in coronary signal-to-noise ratio (p = 0.002).

CONCLUSIONS

Nitroglycerin-enhanced coronary MRA can noninvasively measure coronary artery vasodilation and is a promising noninvasive technique to study coronary vasomotor function.

Evaluation of flow in the left anterior descending coronary artery but not in the left internal mammary artery graft predicts significant stenosis of the arterial conduit

OBJECTIVES

The purpose of this study was to evaluate which Doppler-derived flow index best predicts new distal left anterior descending coronary artery (LAD) stenosis in patients with left internal mammary artery (LIMA) graft.

BACKGROUND

The LIMA flow measurement has been proposed to assess graft function, but it may be misleading in case of new distal LAD stenosis and/or competitive flow from native LAD. Distal LAD coronary flow reserve (CFR: hyperemic/baseline peak flow velocity ratio) may be more appropriate.

METHODS

The LIMA and distal LAD flow was measured by transthoracic Doppler echocardiography in 96 patients undergoing diagnostic/therapeutic coronary angiography, 7 +/- 4 years after cardiac bypass surgery. The LIMA flow indexes (systolic-to-diastolic peak velocity ratio [SDPVr] >1, diastolic time velocity integral fraction [DTVIf] <0.5, and CFR <2) and LAD CFR <2 were used to predict > or =70% new LAD stenosis.

RESULTS

The LAD CFR <2 predicted new LAD stenosis, found in 21 of 77 patients without competitive flow from native LAD, with significantly higher diagnostic accuracy (98%) than LIMA flow indexes (SDPVr >1 = 61%, DTVIf <0.5 = 69%, and CFR <2 = 72%). The LIMA flow indexes were abnormal in 17 of 19 patients with competitive graft flow, but only 5 had graft restriction, and none had significant LAD stenosis. In a multivariate model of new distal LAD stenosis prediction, competitive flow from native LAD reduced the predictive role of LIMA but not of LAD CFR.

CONCLUSIONS

In patients without competitive flow from native LAD, LAD CFR is more accurate for the detection of LAD stenosis than LIMA CFR. In patients with competitive graft flow, abnormal LIMA flow patterns and blunted LIMA CFR do not reflect downstream LAD flow as LAD CFR does.

Quantitative Assessment of Regional Myocardial Flow Reserve Using Tc-99m-Sestamibi Imaging-Comparison With Results of O-15 Water PET-

BACKGROUND

The aims of this study were to develop a method for quantitative estimation of the myocardial blood flow index (MBFI) and myocardial flow reserve (MFR) of the whole left ventricle using (99m)technetium (Tc-99m)-sestamibi imaging.

METHODS AND RESULTS

Twenty-two patients with suspected coronary artery disease and 7 controls underwent both Tc-99m-sestamibi imaging and O-15 water positron emission tomography (PET). The global MBFI was calculated on the basis of the microsphere model from the ratio of the myocardial count to the area under the time - activity curve on the aortic arch. The regional MBFI was calculated from the relative distributions of Tc-99m-sestamibi uptake values. The regional MBFI and MFR (Tc-MFR) obtained using single-photon emission computed tomography were compared with the myocardial blood flow (MBF) and MFR (PET-MFR) obtained using PET as the gold standard. Regional MBFI significantly correlated with the MBF obtained using PET. Regional Tc-MFR also correlated with the regional PET-MFR, with some underestimation.

CONCLUSION

These results indicate that regional MBF and MFR may be estimated by dynamic Tc-99m-sestamibi imaging and can be used for the early detection and estimation of the functional severity of coronary lesions without the need for a PET camera.

Assessment of coronary flow velocity reserve by noninvasive transthoracic Doppler echocardiography in patients with angiographically normal coronary arteries

The measurement of coronary flow velocity reserve (CFVR) by transthoracic Doppler echocardiography (TTDE) with invasive intracoronary Doppler flow wire technique (ICD) was validated and the pathological factors which influence CFVR in patients with angiographically normal coronary arteries were analyzed. CFVR was determined successfully in left anterior descending artery (LAD) in 37 of 40 patients with angiographically normal coronary arteries (men 22, women 15, age 20-75 years, mean age 54 +/- 12 years). Coronary flow velocity was measured in the distal LAD by TTDE with contrast enhancement at baseline and during intravenous adenosine infusion of 140 microg/kg per min within 48 h after ICD technique. Average peak velocity at baseline (APVb), average peak velocity during hyperemia (APVh) and CFVR determined from TTDE were correlated closely with those from ICD measurements (APVb: y = 0.64x + 5.04, r = 0.86, P < 0.001; APVh: y = 0.63x + 14.36, r = 0.82, P < 0.001; CFVR: y = 0.65x + 0.92, r = 0.88, P < 0.001). For CFVR measurements, the mean differences between TTDE and ICD methods were 0.12 +/- 0.39. CFVR in patients with history of hypertension was significantly lower than that in patients without history of hypertension (P < 0.05). Intravascular ultrasound (IVUS) was performed in 34 patients. Plaque formation was found in LAD by IVUS in 17 (50%) patients. No significant difference in CFVR was found between the patients without plaque formation (3.11 +/- 0.49) and those with plaque formation (2.76 +/- 0.53, P = 0.056). It is suggested that TTDE with contrast enhancement provides reliable measurement of APV and CFVR in the distal LAD. The early stage of atherosclerosis could be detected by IVUS, which may be normal in angiography. CFVR is impaired in patients with history of hypertension compared with that in patients without history of hypertension.

Correlation Between Distal Left Anterior Descending Artery Flow Velocity by Transthoracic Doppler Echocardiography and Corrected TIMI Frame Count Before Mechanical Reperfusion in Patients With Anterior Acute Myocardial Infarction

BACKGROUND

This study was designed to determine the utility of transthoracic Doppler echocardiography (TTDE) in evaluating angiographic Thrombolysis in Myocardial Infarction (TIMI) frame count as a quantitative index of coronary reperfusion in patients with anterior acute myocardial infarction (AMI) before mechanical reperfusion.

METHODS AND RESULTS

Color and pulsed TTDE was performed to evaluate distal left anterior descending coronary artery (LAD) reperfusion in 56 consecutive patients with a first anterior AMI before coronary intervention, and these findings were compared with the corrected TIMI frame count (cTFC) by subsequent angiography. Twenty-four of the 56 patients had LAD reperfusion (TIMI 2 or 3) by angiography. Visual antegrade distal LAD flow by color TTDE was detected in 21 of these 24 patients. In the 21 patients, diastolic peak velocity of the distal LAD flow by pulsed TTDE showed a significant correlation with cTFC by angiography (r = -0.74, p < 0.001). The diagnosis of high risk with angiographic cTFC >40 by distal LAD peak velocity <21 cm/s using TTDE had a sensitivity, specificity, and accuracy of 82%, 93%, and 91%, respectively.

CONCLUSION

TTDE enables noninvasive and quantitative evaluation of distal LAD reperfusion in patients with anterior AMI in the acute phase before mechanical reperfusion.

Value of acceleration flow in the left anterior descending coronary artery for the detection of coronary artery stenosis by transthoracic coronary color Doppler echocardiography

Whether the localized flow acceleration occurs in the resting stenotic left anterior descending coronary artery was explored and its value for detection of coronary stenosis estimated. Blood flow in the left anterior descending coronary arteries in 45 patients was detected by transthoracic color Doppler echocardiograph and multipoint pulse Doppler spectrums were recorded in the same segment. The ratio of the maximal peak diastolic velocity to the minimal peak diastolic velocity was calculated. The ratio > or = 1.5 was the cutoff value for the presence of localized acceleration flow. There were 23 patients with localized acceleration flow examined by echocardiography. Twenty of them were found to have luminal diameter stenosis (60% - 98%) in the left anterior descending coronary arteries by coronary angiography and 3 patients were normal. There were 22 patients without localized acceleration flow examined by echocardiography. Eighteen of them had no or < 60% stenosis. Four patients had serious stenosis (> or = 95%) or occluded segments in the left anterior descending coronary arteries on coronary angiography. The ratio of the maximal peak diastolic velocity to the minimal peak diastolic velocity was significantly higher in patients with left anterior descending coronary artery stenosis than that in those without stenosis (1.9 +/- 0.3 vs 1.3 +/- 0.2, P < 0.01) and it correlated significantly with left anterior descending coronary artery stenosis (r = 0.77, P < 0.01). The specificity by using the ratio > or = 1.5 for stenosis detection was 85.7% (18/ 21), and the sensitivity was 83.3% (20/24). This study demonstrated that local blood flow velocity was increased in the resting stenotic left anterior descending coronary artery. Transthoracic color Doppler echocardiography is a reliable noninvasive method to detect localized acceleration flow in the left anterior descending coronary artery stenosis and it is useful in the noninvasive diagnosis of stenosis in the left anterior descending coronary artery.

Transthoracic coronary flow reserve and dobutamine derived myocardial function: a 6-month evaluation after successful coronary angioplasty

After percutaneous transluminal coronary angioplasty (PTCA), stress-echocardiography and gated single photon emission computerized tomography (g-SPECT) are usually performed but both tools have technical limitations. The present study evaluated results of PTCA of left anterior descending artery (LAD) six months after PTCA, by combining transthoracic Doppler coronary flow reserve (CFR) and color Tissue Doppler (C-TD) dobutamine stress.

Six months after PTCA of LAD, 24 men, free of angiographic evidence of restenosis, underwent standard Doppler-echocardiography, transthoracic CFR of distal LAD (hyperemic to basal diastolic coronary flow ratio) and C-TD at rest and during dobutamine stress to quantify myocardial systolic (S_m) and diastolic (E_m and A_m, E_m/A_m ratio) peak velocities in middle posterior septum. Patients with myocardial infarction, coronary stenosis of non-LAD territory and heart failure were excluded. According to dipyridamole g-SPECT, 13 patients had normal perfusion and 11 with perfusion defects. The 2 groups were comparable for age, wall motion score index (WMSI) and C-TD at rest. However, patients with perfusion defects had lower CFR (2.11 ± 0.4 versus 2.87 ± 0.6, p < 0.002) and septal S_m at high-dose dobutamine (p < 0.01), with higher WMSI (p < 0.05) and stress-echo positivity of LAD territory in 5/11 patients. In the overall population, CFR was related negatively to high-dobutamine WMSI (r = -0.50, p < 0.01) and positively to high-dobutamine S_m of middle septum (r = 0.55, p < 0.005).

In conclusion, even in absence of epicardial coronary restenosis, stress perfusion imaging reflects a physiologic impairment in coronary microcirculation function whose magnitude is associated with the degree of regional functional impairment detectable by C-TD.

Nebivolol improves coronary flow reserve in hypertensive patients without coronary heart disease

OBJECTIVE

To examine the effects of nebivolol, a beta-blocker with nitroxide-mediated vasodilating properties, on coronary flow reserve (CFR) in patients with uncomplicated arterial hypertension.

DESIGN, SETTING AND PATIENTS

Fourteen newly diagnosed, never-treated, World Health Organization grade I-II hypertensive patients (male/female, 10/4; mean age, 47 years), free of coronary heart disease, underwent standard Doppler echocardiography and determination of CFR in the distal left anterior descending artery by low-dose dipyridamole (0.56 mg/kg intravenously in 4 min) at baseline and after 4 weeks of treatment with 5 mg nebivolol once daily.

RESULTS

At baseline, nine patients had left ventricular (LV) hypertrophy (LV mass index > or = 51 g/m). After 4 weeks of therapy, the blood pressure was decreased from 148 +/- 8.1/101.4 +/- 4.6 mmHg to 140.7 +/- 7.0/91.1 +/- 7.4 mmHg and end-systolic stress was also significantly reduced. Heart rate was reduced (P <0.01), whereas LV end-diastolic diameter and stroke volume tended to increase (P=0.07 and P=0.09, respectively). No changes were detected in the LV mass index, relative wall thickness, fractional shortening and LV diastolic properties. Both resting and dipyridamole rate-pressure products were lower after nebivolol but dipyridamole-induced changes were not influenced by the therapy. In contrast, nebivolol therapy did not alter coronary velocities at rest, but caused a greater increase in coronary velocities after dipyridamole (P <0.03), leading to a greater CFR (2.12 +/- 0.33 versus 1.89 +/- 0.31, P <0.0001). Nebivolol induced an absolute increase of 8% in the CFR in nine of 14 patients (64.3%).

CONCLUSIONS

In hypertensive patients free of coronary artery disease, 4-week nebivolol therapy induces a significant increase of the CFR. Nebivolol preserves coronary flow at rest despite the reduction of metabolic (O2 consumption) and hemodynamic (diastolic blood pressure) determinants. The increase of hyperemic coronary velocities appears due to the reduction of coronary resistance.

[Measurement of coronary flow and flow reserve with transthoracic echocardiography: an old concept, a new tool, a lot of applications]

Non invasive evaluation of coronary flow and flow reserve by using transthoracic echocardiography is a promising method for evaluating coronary disease. Left anterior descending and right posterior descending coronary flow are accessible in the majority of patients. This technique is useful in various settings: detection of coronary artery stenosis, coronary occlusion, follow up after percutaneous coronary intervention, evaluation of the significance of coronary stenosis of intermediate severity, evaluation of the microcirculation, study of reperfusion and no reflow in the acute phase of myocardial infarction, evaluation of bypass grafts, improvement of the diagnostic accuracy during stress echocardiography. After a period of training, it's possible to change an old concept, formerly not easily accessible in clinical practice, into a useful and modern tool for evaluating coronary artery disease.

Measurement of coronary vasomotor function: getting to the heart of the matter in cardiovascular research

Measurement of endothelial function in patients has emerged as a useful tool for cardiovascular research. Although no gold standard for the measurement of endothelial function exists, the measurement of flow-mediated dilation in the brachial artery, assessed with Doppler ultrasonography, is the most studied method. However, the assumption that endothelial dysfunction detected in brachial arteries is a manifestation of systemic endothelial dysfunction including the coronary circulation may not be entirely valid. Brachial and myocardial circulations differ in terms of the microvascular architecture, the pattern of blood flow and vascular resistance (e.g. shunt vessels occur in the hand but not in the myocardium), their metabolic regulation, type of receptors that contribute to humoral regulation and the pathways that are activated to induce hyperaemia. In this context, measuring coronary vasomotor function may be more useful than brachial artery measures to predict and assess potential myocardial damage related to limited vascular responsiveness. This review aims to provide an overview of the basic concept of coronary flow reserve and its different modalities of measurement, as well as its utility in cardiovascular research.

Early assessment of coronary flow reserve by transthoracic Doppler echocardiography predicts late remodeling in reperfused anterior myocardial infarction

BACKGROUND

Microvascular integrity is an essential determinant of favorable late outcome in reperfused myocardial infarction. Coronary flow reserve (CFR) can be assessed by transthoracic Doppler echocardiography and provides a functional estimate of microvascular integrity downstream from the patent infarct-related vessel.

OBJECTIVE

We sought to assess the effects of CFR in predicting late left ventricular (LV) remodeling in patients with reperfused acute anterior myocardial infarction treated with primary angioplasty.

METHODS

In all, 31 patients admitted with acute anterior myocardial infarction underwent primary angioplasty of the infarct-related vessel. After angioplasty, angiographic thrombosis in myocardial infarction (TIMI) grade and myocardial blush were scored. On the first day, all underwent stress echocardiography and CFR evaluation of left anterior descending coronary artery by transthoracic Doppler. All patients had resting 2-dimensional echocardiography at 1, 3, and 6 months for assessment of LV function.

RESULTS

CFR could be successfully assessed in 31 patients. After 6 months 5 patients showed LV dilatation (group I), whereas 26 patients did not show significant variation (group II). On day 1, CFR was higher (group I = 1.43 +/- 0.11 vs group II = 1.67 +/- 0.26, P =.005) and the deceleration time of diastolic left anterior descending coronary artery flow velocity was longer (group I = 212 +/- 41.4 milliseconds vs group II = 286 +/- 106.7 milliseconds, P <.02) in patients without, compared with those with LV remodeling, whereas there was no difference in angiographic parameters.

CONCLUSION

Early assessment of CFR and the pattern of baseline diastolic coronary flow velocity by transthoracic Doppler echocardiography is feasible, safe, and more useful than angiographic indices in identifying patients at high risk of remodeling in spite of successful primary angioplasty.

Noninvasive coronary flow velocity reserve measurement in the posterior descending coronary artery for detecting coronary stenosis in the right coronary artery using contrast-enhanced transthoracic Doppler echocardiography

BACKGROUND

Coronary flow velocity reserve (CFVR) measurement by transthoracic Doppler echocardiography (TTDE) has been found to be useful for assessing left anterior descending coronary artery (LAD) stenosis. However, this method has been restricted only for the LAD. The purpose of this study was to detect severe right coronary artery (RCA) stenosis by CFVR measurement using contrast-enhanced TTDE.

METHODS

In 60 consecutive patients with angina pectoris (mean (SD) age: 60 (11), 18 women), coronary flow velocities in the RCA were recorded in the postero-descending coronary artery by contrast-enhanced TTDE at rest and during hyperemia induced by intravenous infusion of adenosine triphosphate (140 mcg/ml/kg). CFVR was calculated as the ratio of hyperemic to basal peak and mean diastolic flow velocity. CFVR measurements by TTDE were compared with the results of coronary angiography performed within 1 week.

RESULTS

Coronary flow velocity was successfully recorded in 49 (82%) of the 60 patients with contrast agent. CFVR (mean (SD)) was 1.4 (0.4) in patients with, and 2.6 (0.6) in patients without significant stenosis in the RCA (%diameter stenosis > 75%, P < 0.001). Using the cutoff value 2.0 for CFVR in the RCA, its sensitivity and specificity in detecting significant stenosis in the RCA were 88% and 91%, respectively.

CONCLUSION

CFVR measurement in the postero-descending coronary artery by contrast enhanced TTDE is a new, noninvasive method to detect significant stenosis in the RCA.

Evaluation of Improved Coronary Flow Velocity Reserve Using Transthoracic Doppler Echocardiography After Single LDL Apheresis

The purpose of this study was to clarify whether coronary flow velocity reserve (CFVR), evaluated by adenosine 5'-triphosphate-induced hyperemia, is improved by single low-density lipoprotein (LDL) apheresis. Lipid lowering therapy is known to improve endothelium-dependent vasodilatation in forearm or coronary resistant vessels. However, few reports have studied the effect of acute LDL reduction on CFVR.

METHODS

Seven patients with familial hypercholesterolemia and significant coronary stenosis except in the left anterior descending artery (LAD) were enrolled in this study. Coronary flow velocity reserve was estimated before and after LDL apheresis using transthoracic Doppler echocardiography (TTDE), which detects the flow velocity at the distal site of the LAD. Although the averaged diastolic peak velocity (ADPV) during ATP-induced hyperemia was similar before and after LDL apheresis, the ADPV at baseline decreased from 30.69 to 25.56 cm/s, resulting in an increased CFVR from 1.78 to 2.10 (P < 0.001). Plasma bradykinin and 6 keto PGF1alpha increased while fibrinogen and plasma viscosity decreased after apheresis. Single LDL apheresis improves CFVR according to TTDE analysis because of the decreasing ADPV at baseline, which is thought to be induced by epicardial coronary artery dilatation and improved microvessel function. This is the result of various factors, such as changes in plasma LDL cholesterol, bradykinin and PGI2 levels with LDL apheresis.

Coronary flow reserve of the angiographically normal left anterior descending coronary artery in patients with remote coronary artery disease

Coronary artery disease (CAD) has been suggested to alter coronary flow reserve (CFR; the ratio between hyperemic and baseline coronary flow velocities) not only in territories supplied by stenotic arteries but also in angiographically normal, remote regions. However, few data exist regarding the left anterior descending (LAD) coronary artery as the normal index artery. The influence of remote CAD on CFR of the angiographically normal LAD was evaluated with transthoracic Doppler ultrasound to measure CFR in the LAD during 90 seconds of venous adenosine infusion (140 microg/kg/min) in 122 subjects who were assigned to 1 group; group 1 comprised 49 controls without angiographically detectable CAD, and group 2 consisted of 73 patients with an angiographically normal LAD and remote CAD. Group 2 was divided into 4 subgroups: 16 patients with previous remote percutaneous coronary intervention (group 2A); 13 patients with significant remote stenosis (group 2B); 23 patients with previous remote myocardial infarction and percutaneous coronary intervention (group 2C); and 21 patients with previous remote myocardial infarction but no percutaneous coronary intervention (group 2D). CFR in the LAD was not significantly different in groups 1 and 2 (3.08 +/- 0.61 and 3.03 +/- 0.69, respectively, p = NS). Decreased ejection fraction and increased wall motion score index in patients with remote CAD (p < 0.00001) and multivessel CAD did not affect CFR in the LAD (group 2A 3.18 +/- 0.77; group 2B 3.05 +/- 0.65; group 2C 3.07 +/- 0.79; group 2D 2.86 +/- 0.50, respectively; F = 0.63, p = NS). In conclusion, CFR of an angiographically normal LAD is preserved in patients with remote CAD, even in the presence of previous remote myocardial infarction and wall motion abnormalities.

Surgical revascularization of coronary bifurcations employing a single arterial graft according to the "omega-anastomosis" technique: initial experience

OBJECTIVES

The aim of this study was to evaluate the early postoperative outcome in patients undergoing "omega-anastomosis" construction, a technique that permits revascularization of coronary bifurcations employing a single arterial graft.

MATERIALS AND METHODS

Between January 2000 and March 2002, omega-anastomosis was employed in 12 patients. The main indication for omega-anastomosis construction was the presence of a significant stenotic lesion involving one of the coronary tree's bifurcations, presenting a relevant secondary branch. There were ten men and two women, with a mean age of 55.4 +/- 4.3 years (range 48 to 66). The omega-anastomosis was constructed employing a single arterial graft (internal mammary artery or radial artery) effectively tailored to obtain a bi-petal shape and anastomosed to the coronary bifurcation according to a three-foliate anastomosis. All patients underwent postoperative coronary angiography.

RESULTS

There were no hospital deaths, neither ECG nor enzymatic alterations. One patient was reoperated for excessive bleeding. The mean aortic cross-clamp time and duration of CPB (cardiopulmonary bypass) were 64 +/- 18 minutes (range 45 to 108) and 89 +/- 26 minutes (range 67 to 135), respectively. Thirty-four arterial conduits were used: 12 LIMA, 12 RIMA, and 10 RA. Twelve omega-anastomoses were constructed, in six patients employing the RA, and in six other patients employing one of the internal mammary arteries (IMAs). Five left Y-grafts between the in situ LIMA and free LIMA graft and one right Y-graft between the RIMA and RA were constructed. The mean ICU stay was 14.4 +/- 5.7 hours. The postoperative coronary angiography revealed a good patency of the "omega-anastomosis." Transthoracic color Doppler echocardiography (TTECD) demonstrated a normal IMAs flow pattern in all cases.

CONCLUSIONS

We define the reported configuration as a possible surgical alternative to achieve total arterial myocardial revascularization in multi-vessels patients, associated with excellent postoperative outcome that should be part of the coronary surgical armamentarium.

Semiautomatic detection of left ventricular contours in contrast-enhanced echocardiographic images: Comparison with magnetic resonance imaging

The aim of this study was to evaluate the accuracy of a semiautomatic contour detection method for left ventricular (LV) volume calculation in contrast-enhanced echocardiographic images. In 26 patients, LV volumes were automatically measured by magnetic resonance imaging and second harmonic echocardiography after intravenous Levovist administration. LV cavity edges were manually drawn and semiautomatically outlined using the active contour algorithm, improved by a nonlinear anisotropic filter; LV volumes were calculated by the modified Simpson's rule. Manual and semiautomatic analysis of echocardiographic images lasted 45 +/- 6 and 20 +/- 8 seconds, respectively. Contrast echocardiography volumes were smaller than those by magnetic resonance imaging (mean difference: 16 mL for manual and 18 mL for automatic analysis). LV volumes by echocardiography closely related with those by magnetic resonance imaging using both manual (r = 0.955) and semiautomatic (r = 0.945) analysis; the correlation was closer for end-systolic than for end-diastolic volumes. In conclusion, this method provides a fast measure of LV volumes in contrast-enhanced images while reducing operator dependency.

Advances in myocardial contrast echocardiography and the role of adenosine stress

Advances in contrast echocardiography hold promise for the routine assessment of myocardial perfusion. Continued progress may ultimately position myocardial contrast echocardiography (MCE) as an imaging modality that can provide comprehensive cardiac assessment-anatomic, physiologic, and pathophysiologic. Vasodilator stress with adenosine can play an important role in conjunction with MCE, particularly as it relates to the noninvasive evaluation of myocardial perfusion and coronary blood flow reserve. Adenosine pharmacologic stress testing may provide improved test performance through perfusion detection when compared with traditional use of dobutamine assessments of regional wall motion abnormalities.

Contrast for vascular imaging

This article discusses the use of standard contrast agents that, when coupled with high-resolution carotid ultrasound, offers the dramatic potential to improve measurement of intimal medial thickness, better defining luminal endothelial surface, improving the determination of plaque ulceration, and offering the dramatic capabilities to visualize directly neovasculature growth of the vasa vasorum. The technique may identify vulnerable plaques and may also show their alterations with therapeutic pharmacologic interventions. In the coronary circulation, use of contrast significantly enhances the ability to image the epicardial coronary arteries to obtain data on coronary flow reserve for the diagnosis of coronary artery disease.

Measurement of coronary flow velocity reserve in the posterior descending coronary artery by contrast-enhanced transthoracic Doppler echocardiography

BACKGROUND

Although the measurement of coronary flow velocity (CFV) reserve (CFVR) in the left anterior descending coronary artery (LAD) by transthoracic Doppler echocardiography has been established, its success rate in the posterior descending coronary artery (PD) is still limited.

OBJECTIVE

This study reports the feasibility and diagnostic accuracy of measuring CFVR in the PD by transthoracic Doppler echocardiography.

METHODS

CFVR in both the distal LAD and the PD was measured in 151 consecutive patients before coronary angiography. PD flow was investigated under the guidance of a nondirectional Doppler color flow map with harmonic imaging in the modified apical 2-chamber view. Intravenous contrast agent, Levovist, was injected to enhance the CFV envelope at baseline and during hyperemia.

RESULTS

CFVR was obtained in 145 patients in the LAD and 126 patients in the PD (P <.001). The success rate of CFVR measurement in the PD was significantly higher in the last 50 patients (88%) than it was in the first 50 patients (72%) (P <.05). CFVR in the PD was significantly lower for patients with significant stenosis of the artery supplying the PD than it was in those without stenosis (1.58 +/- 0.59 vs 2.45 +/- 0.72, P <.001). CFVR in the distal LAD was 1.40 +/- 0.62 in patients with significant LAD stenosis and 2.45 +/- 0.80 in those without stenosis (P <.001). If a cut-off value of CFVR < 2 was used, sensitivity, specificity, and accuracy for the diagnosis of significant (>50%) stenosis of the artery supplying the PD were 84%, 83%, and 83%, respectively, whereas for the LAD they were 91%, 75%, and 80%, respectively.

CONCLUSIONS

Noninvasive measurement of CFVR in the PD could be obtained in the majority of unselected patients using a nondirectional Doppler color flow map and contrast-enhanced harmonic imaging. The diagnostic accuracy of CFVR in the PD is similar to that of the LAD and, hence, has a potential clinical use.

Coronary artery diameter can be assessed reliably with transthoracic echocardiography

We studied whether diameters of coronary arteries can be measured accurately with the use of transthoracic echocardiography (TTE). By knowing the anatomic diameter of the coronary artery together with coronary flow velocity it is possible to measure coronary flow volume more precisely by TTE. However, the suitability of TTE for measurement of diameters of all main epicardial coronary arteries has not been systematically validated. We measured the diameters of the left main (LM), left anterior descending (LAD), left circumflex (LCX), and right coronary arteries (RCA) with the use of TTE [manual two-dimensional (2D), color-Doppler, and automated 2D analysis] in 30 patients who had normal coronary anatomy. We compared these diameters to those measured with quantitative coronary angiography (QCA). We could measure diameters of LM, LAD, LCX, and RCA by TTE in up to 37%, 63%, 7%, and 60% of patients, respectively. The overall correlation coefficients between TTE and QCA measurements were 0.83 ( P < 0.01) with manual 2D analysis, 0.82 ( P < 0.01) with automated 2D analysis, and 0.94 ( P < 0.01) with a color-Doppler-based analysis. Interobserver variability of TTE measurements was low (coefficient of variation 5.4 ± 4.6–7.5 ± 8.8%). TTE is an accurate method to evaluate coronary artery diameter in patients with healthy coronary arteries.

Demonstration of coronary artery flow using transthoracic Doppler echocardiography

Transthoracic Doppler echocardiography is emerging as a promising method for evaluating coronary artery disease. After a period of training, detection and measurement of distal left anterior descending coronary artery flow with transthoracic Doppler echocardiography is feasible in more than 90% of the patients. Using transthoracic Doppler echocardiography with a high-frequency transducer and special setting of low Nyquist limits, pathologic coronary flow dynamics can be demonstrated. Measurement of coronary flow reserve may impact diagnosis or clinical treatment in those: (1) with anginal chest pain and angiographically normal coronary arteries; (2) with intermediate-grade coronary obstruction where the physiologic significance is in doubt; and (3) who have had an attempt at revascularization and the effectiveness of the therapy is uncertain.

Enhanced coronary flow velocity during intra-aortic balloon pumping assessed by transthoracic doppler echocardiography

OBJECTIVES

The study was done to determine potential utility of measuring coronary flow velocity (CFV) by transthoracic Doppler echocardiography (TTDE) during intra-aortic balloon pumping (IABP).

BACKGROUND

Use of IABP has been shown to increase CFV assessed by an invasive technique. The CFV in the left anterior descending coronary artery (LAD) can be measured by TTDE.

METHODS

Coronary flow velocity in the distal LAD by TTDE was measured in 40 critically ill patients requiring IABP. All patients received emergency coronary angiography. Both CFV and pressure data were obtained during 1:2 balloon pumping.

RESULTS

Adequate diastolic CFV recording was obtained in all patients. The IABP decreased systolic pressure and increased diastolic pressure. Average peak diastolic flow velocity and diastolic velocity time integral was 19 +/- 11 cm/s and 7.7 +/- 4.4 cm with non-augmented beat. These values were increased significantly (61 +/- 38%, 59 +/- 35%, p < 0.001) with augmented beat. Significant correlation was noted between % diastolic pressure augmentation and % increase in diastolic CFV (r = 0.62 to 0.69, p < 0.001). There was no significant difference in flow enhancement during IABP, irrespective to the proximal LAD stenosis severity (severe stenosis: 73 +/- 70%; intermediate stenosis: 61 +/- 29%; no significant stenosis: 58 +/- 29%; p = NS, analysis of variance). By continuous recording of CFV, the optimal timing of balloon control could be adjusted to maximize flow velocity during augmentation.

CONCLUSIONS

Use of TTDE can be employed in monitoring CFV augmentation during IABP. The IABP produced significant distal flow enhancement even in patients with critical proximal stenosis. This totally noninvasive approach may help to optimize the benefits of IABP for coronary flow augmentation.

Simple detection of occluded coronary artery using retrograde flow in septal branch and left anterior descending coronary artery by transthoracic doppler echocardiography at rest

BACKGROUND

We hypothesized that coronary flow assessment by transthoracic Doppler echocardiography (TTDE) for both intramyocardial collateral channel and epicardial channels would be useful for identifying occluded left anterior descending coronary artery (LAD).

METHODS

We assessed flow direction in the LAD and the septal branch (SEP) by TTDE in 302 consecutive patients who were suggested to have ischemic heart disease. We defined antegrade LAD flow as a direction from the base to the apex of the left ventricle in the anterior groove area, and antegrade SEP flow as a direction from anterior to inferior in the anterior interventricular septum. By contrast, we defined retrograde LAD and SEP flow as an inverse direction. We performed angiography on all patients.

RESULTS

Retrograde flow was detected in 22 (LAD, 16 patients; SEP, 6 patients) of 23 patients with occluded LAD, and antegrade flow was detected in all patients without occluded LAD. The sensitivity and specificity for identification of occluded LAD by TTDE were 96% and 100%, respectively.

CONCLUSIONS

Assessment of flow direction in both LAD and SEP by TTDE is a useful method in identification of occluded LAD.

Emerging, noninvasive surrogate markers of atherosclerosis

Noninvasive surrogate markers of atherosclerosis allow the physician to identify subclinical disease before the occurrence of adverse cardiovascular events, thereby limiting the need to perform invasive diagnostic procedures. Imaging modalities, such as carotid artery ultrasound, two-dimensional echocardiography, coronary artery calcium imaging, cardiac magnetic resonance imaging, ankle-brachial indices, brachial artery reactivity testing, and epicardial coronary flow reserve measurements, provide information that may improve the predictive value of a person's risk of developing clinically significant atherosclerotic disease. Newer imaging modalities have also emerged to bring insight into the pathophysiology and treatment of atherosclerosis.

Feasibility and safety of transeophageal atrial pacing stress echocardiography in patients with known or suspected coronary artery disease

To investigate the feasibility and safety of the transesophageal atrial pacing stress test combined with echocardiography (TAPSE) 1,727 TAPSE tests were performed on 1,641 patients consecutively referred to our echocardiographic laboratory for nonexercise stress testing (1,319 men; mean age 60 +/- 9 years; 34% of whom were outpatients). Wall motion abnormalities were present at baseline echocardiography in 975 cases (56%). TAPSE was feasible in 1,648 cases (95.4%). It was not feasible in 79 patients due to failure of positioning the transnasal catheter (n=11), the patient's intolerance of esophageal stimulation (n=24), failure to obtain any or stable atrial capture (n=36), or because the echocardiogram could not be evaluated at the peak of the test (n=8). TAPSE was diagnostic in 1,584 cases (96% of the feasible tests, 92% of all attempts). TAPSE was nondiagnostic in 64 cases (4% of the feasible tests) due to second-degree atrioventricular type I block resistance to atropine administration with failure to achieve 85% of the age-predicted maximum heart rate (n=59) or due to side effects, such as arrhythmias (n=3) or hypertension (n=2), which required premature interruption of the test. There were no major complications (death, myocardial infarction, or life-threatening arrhythmias). There were 28 instances of minor complications that comprised transient arrhythmias, including atrial fibrillation (n=8), paroxysmal supraventricular tachycardia (n=6), automatic atrial tachycardia (n=1), sinus arrest (n=1), atrioventricular junctional rhythm (n=2), ectopic atrial rhythm (n=2), nonsustained ventricular tachycardia (maximum 6 beats, n=3), hypotension (n=1), and hypertension (n=4) leading to interruption of the test. Only 5 complications hampered a diagnostic result, whereas 18 occurred during or after a positive test and 5 during a negative, but diagnostic, test. Thus, TAPSE is a highly feasible and very safe stress test. It gives high percentage of diagnostic tests and may represent a valid alternative to pharmacologic stressors.

Cut-off value of coronary flow velocity reserve by transthoracic Doppler echocardiography for diagnosis of significant left anterior descending artery stenosis in patients with coronary risk factors

The purpose of this study was to evaluate the adequate cut-off value of coronary flow velocity reserve (CFVR) with transthoracic Doppler echocardiography for diagnoses of significant left anterior descending (LAD) artery stenosis in a large study population with various coronary risk factors. CFVR, which has been used for evaluation of significant coronary artery stenosis, can be reduced despite angiographically normal coronary arteries in patients with various coronary risk factors. However, the adequate cut-off value of CFVR for diagnosing significant LAD stenosis has not been fully established in patients with coronary risk factors. We examined 138 consecutive patients who underwent coronary angiography. Clinical histories of coronary risk factors were determined from interviews or medical records. CFVR assessment in the LAD artery by transthoracic Doppler echocardiography was performed in all patients. Of the 138 patients, 30 had significant stenosis, and the remainder had no stenotic lesions in the LAD artery. Receiver-operating characteristic curves for detection of significant LAD stenosis showed that a cut-off value of <2.0 was extremely precise. A cut-off value <2.0 of CFVR had a sensitivity of 90%, a specificity of 93%, a positive predictive value of 77%, and a negative predictive value of 97% for the presence of significant LAD stenosis. A cut-off value <2.0 of CFVR by transthoracic Doppler echocardiography was adequate for the diagnosis of significant LAD stenosis in a population that included patients with coronary risk factors.

Noninvasive assessment of myocardial ischemia in the left ventricular inferior regions by coronary flow reserve measurement using transthoracic doppler echocardiography

OBJECTIVE

The purpose of this study was to evaluate the potential of noninvasive measurement of coronary flow reserve (CFR) by transthoracic Doppler echocardiography (TTDE) for the assessment of myocardial ischemia in the left ventricular (LV) inferior regions.

BACKGROUND

Although coronary flow assessment by TTDE has been determined for the assessment of perfusion abnormality in the LV anterior regions, the usefulness of this method has not been well investigated in the LV inferior regions.

METHODS

We studied 50 patients (43 men; mean age 60 +/- 9 years) with suggested coronary artery disease. CFR in the posterodescending coronary artery (PDA) was calculated as a ratio of hyperemic to basal peak (peak CFR) and mean (mean CFR) flow velocities in the PDA, which were measured by TTDE. CFR values were compared with the results of exercise 201-thallium single photon emission computed tomography.

RESULTS

CFR was successfully measured in 43 of 50 patients (86%). Mean and peak CFR < 2 were shown in 10 of 12 patients with abnormal perfusion in the LV inferior regions, whereas CFR > or = 2 were shown in 30 of 31 patients with normal perfusion. Thus, CFR < 2 in the PDA by TTDE had a sensitivity of 83% and a specificity of 97% for the assessment of perfusion abnormality in the LV inferior regions by 201-thallium single photon emission computed tomography.

CONCLUSIONS

CFR in the PDA measured by TTDE provides data equivalent to those obtained by 201-thallium single photon emission computed tomography for myocardial ischemia in the LV inferior regions.

Imaging of all three coronary arteries by transthoracic echocardiography. An illustrated guide

Background

Improvements in ultrasound technology has enabled direct, transthoracic visualization of long portions of coronary arteries : the left anterior descending (LAD), circumflex (Cx) and right coronary artery (RCA). Transthoracic measurements of coronary flow velocity were proved to be highly reproducible and correlated with invasive measurements. While clinical applications of transthoracic echocardiography (TTE) of principal coronary arteries are still very limited they will likely grow. The echocardiographers may therefore be interested to know the ultrasonic views, technique of examination and be aware where to look for coronary arteries and how to optimize the images.

Methods

A step-by-step approach to direct, transthoracic visualization of the LAD, Cx and RCA is presented. The technique of examination is discussed, correlations with basic coronary angiography views and heart anatomy are shown and extensively illustrated with photographs and movie-pictures. Hints concerning optimization of ultrasound images are presented and artifacts of imaging are discussed.

Conclusions

Direct, transthoracic examination of the LAD, Cx and RCA in adults is possible and may become a useful adjunct to other methods of coronary artery examination but studies are needed to establish its role.

Coronary flow reserve in hypertensive patients with appropriate or inappropriate left ventricular mass

OBJECTIVE

To assess the association between coronary flow reserve (CFR) and levels of left ventricular mass (LVM) exceeding the compensatory needs in arterial hypertension. DESIGN, SETTINGS AND PATIENTS: The association between the excess of LV mass and CFR was assessed in a population of 40 consecutive hypertensive outpatients free of coronary heart disease, 22 with appropriate and 17 with inappropriately high LVM (i.e. LVM exceeding 128% of the value predicted by sex, stroke work and height in m(2.7)). The CFR (the ratio between dipyridamole and basal diastolic peak velocity) of the distal left anterior descending artery was measured by transthoracic Doppler echocardiography.

RESULTS

Patients with inappropriate LVM had similar age, body mass index (BMI), baseline blood pressure (BP) and coronary velocities, but lower LV systolic function, post-dipyridamole diastolic peak velocities (P < 0.05) and lower CFR (P < 0.002) than patients with appropriate LVM. CFR was negatively related to the extent of the excess of LVM (beta = -0.44, P < 0.005), independently of potential combined effect of age, BMI and post-dipyridamole diastolic BP. Impairment of CFR (i.e. < 2) was better discriminated by identification of clear-cut inappropriate LVM (P < 0.004) than by the presence of LV hypertrophy (i.e. LV mass index > or = 51 g/m(2.7); P = 0.057).

CONCLUSIONS

In hypertensive patients free of coronary artery disease, the degree of reduction in CFR is associated with the excess of LVM beyond the values compensatory for individual haemodynamic load. This relation is also independent of the presence of LV hypertrophy.

Coronary flow velocity analysis during short term follow up after coronary reperfusion: use of transthoracic Doppler echocardiography to predict regional wall motion recovery in patients with acute myocardial infarction

BACKGROUND

A recent study using a Doppler guide wire showed that coronary flow velocity measurements immediately after coronary reperfusion were useful in predicting recovery of regional left ventricular function. The value of coronary flow velocity analyses during follow up after reperfusion has not been established in the clinical setting.

OBJECTIVE

To evaluate coronary flow velocity measurements in predicting recovery of regional left ventricular function during short term follow up after acute anterior myocardial infarction, using transthoracic Doppler echocardiography (TTDE).

METHODS

30 consecutive patients with anterior acute myocardial infarction were studied. They all underwent successful coronary angioplasty for lesions in the left anterior descending coronary artery (LAD). Using TTDE, coronary flow velocity in the LAD was recorded on days 1 and 3, and at one and two weeks after reperfusion. Regional wall motion was analysed by the wall motion score index (WMSI), calculated as an average of segmental scores in the LAD territory before reperfusion and one month after the infarction.

RESULTS

Deceleration time of diastolic flow velocity (DDT) in patients with viable myocardium (WMSI in LAD territory at one month, < 2.0) was significantly longer after recanalisation than in patients without viable myocardium (WMSI in LAD territory at one month, > 2.0): 657 (226) v 271 (117) ms on day 1, p < 0.001; 732 (219) v 373 (217) ms on day 3, p < 0.01; and 903 (107) v 577 (300) ms at one week, p < 0.01. However, the difference at two weeks (991 (75) v 795 (281) ms) was not significant. For the prediction of viable myocardium, DDT > 600 ms had a sensitivity of 78% and a specificity of 92% on day 1, and a sensitivity of 78% and a specificity of 84% on day 3. At one and two weeks, DDT > 600 ms was sensitive (100% and 100%, respectively) but less specific (46% and 26%, respectively) for predicting viable myocardium.

CONCLUSIONS

Non-invasive assessment of coronary flow velocity using TTDE within three days of successful coronary angioplasty in patients with anterior acute myocardial infarction is useful in predicting recovery of regional left ventricular function.

Detection of early impairment of coronary flow reserve in patients with systemic sclerosis

OBJECTIVE

To investigate whether coronary flow reserve (CFR), measured by a new non-invasive method, is impaired early in patients with systemic sclerosis (SSc) and whether CFR impairment correlates with clinical or functional measures, or both.

METHODS

27 patients with SSc without clinical evidence of ischaemic heart disease and 23 control group subjects matched for age and sex were studied. CFR was evaluated in the left anterior descending coronary artery (LAD) with a new non-invasive method: contrast (Levovist) enhanced transthoracic Doppler during adenosine infusion. The pulsed wave Doppler examination of blood flow velocity was recorded in the LAD at rest and after maximum vasodilatation by adenosine infusion.

RESULTS

In patients with SSc, without clinical evidence of ischaemic heart disease, CFR was impaired (p=0.0001). 14/27 patients with SSc had severe reduction of the CFR (< or =2.5) compared with controls (p=0.002). A non-significant trend between mean CFR and the severity and duration of the disease was also seen.

CONCLUSIONS

CFR is often reduced in patients with SSc, suggesting early preclinical cardiac involvement in SSc. This impairment in coronary microvasculature is detectable by a non-invasive echocardiographic method and in this study was more common in the diffuse form of SSc.

Value of echocardiography in predicting future cardiac events after acute myocardial infarction

Short- and long-term survival after acute myocardial infarction mainly depends on three factors: the amount of myocardium that had become necrotic, the area of myocardium at further risk of becoming necrotic, and the patency of the infarct-related artery. Echocardiography is a low-cost, safe, bedside, repeatable tool, particularly useful for prognostic stratification after myocardial injury. Two-dimensional echocardiography analyzes left ventricular function, the most powerful predictor of survival immediately after acute myocardial infarction. Myocardial contrast echocardiography measures the infarct size and detects viable myocardium. Stress echocardiography stratifies patients with viable myocardium and/or multivessel coronary artery disease who need further diagnostic and therapeutic interventions. Transthoracic coronary Doppler ultrasonography assesses effective recanalization and coronary flow reserve of the left anterior descending coronary artery. Further technologic advances are needed to allow direct noninvasive measurement of flow by transthoracic Doppler ultrasonography in other coronary arteries.

Noninvasive assessment of significant right coronary artery stenosis based on coronary flow velocity reserve in the right coronary artery by transthoracic Doppler echocardiography

BACKGROUND

Coronary flow velocity reserve (CFVR) measured by transthoracic Doppler echocardiography (TTDE) has been reported to be useful for the noninvasive assessment of coronary stenosis in the left anterior descending artery. However, the measurement of CFVR in the right coronary artery by TTDE has not yet been validated in a clinical study.

OBJECTIVE

The aim of this study was to evaluate whether CFVR by TTDE can detect significant stenosis in the right coronary artery.

METHODS

We studied 50 patients who underwent coronary angiography. Coronary flow velocity in the posterior descending branch of the right coronary artery (PD) was measured by TTDE both at baseline and during hyperemia induced by the intravenous infusion of adenosine triphosphate. CFVR was calculated as the hyperemia/baseline (average diastolic peak velocity).

RESULTS

Adequate spectral Doppler recordings in the PD were obtained in 36 patients including 26 patients who were given an echocardiographic contrast agent to improve Doppler spectral signals. The study population was divided into 2 groups with (Group A;n = 11) and without (Group B;n = 25) significant stenosis in the right coronary artery. CFVR in Group A was significantly smaller than that in Group B (1.6+/-0.3versus2.5+/-0.4; P < 0.0001). The sensitivity of a CFVR of <2.0 for predicting the presence of significant stenosis in the right coronary artery was 91%, and the specificity was 88%.

CONCLUSIONS

The measurement of CFVR in the PD by TTDE is useful for the noninvasive assessment of significant stenosis in the right coronary artery.

Characterization of arterial stenosis and elasticity by analysis of high-frequency pressure wave components

We describe a novel method for assessing stenosis severity based on pressure wave measurements. Pressure waves for several degrees of stenosis at different distances proximal to the stenosis were recorded from in vitro and in vivo models. Signal analysis was performed using power spectral density, and radial compliance was also measured. Pressure wave components at the acoustic frequency band (400-2500Hz) changed gradually and were dependent upon the distance from the stenosis and its severity. The shift of the pressure components could also demonstrate the elastic properties of tubes and arteries and explain the effect of a bifurcation in the system.

[Detection of angiographic lesions in the left anterior descending coronary artery by transthoracic Doppler echocardiography: usefulness of non-invasive assessment of coronary flow reserve]

INTRODUCTION

We evaluated the feasibility of detecting blood flow in the left anterior descending coronary artery and the usefulness of measuring coronary flow reserve to diagnose significant coronary artery disease, both by means of transthoracic Doppler echocardiography using a high-frequency transducer and echo-contrast agent.

PATIENTS AND METHOD

We studied 107 patients who were scheduled for coronary arteriography for known or suspected ischemic heart disease. A Doppler signal was recorded by a pulsed wave in the distal left anterior descending artery at baseline and after dipyridamole infusion. An echo-contrast agent was administered to all patients. A coronary flow reserve equal to or higher than 1.7 was considered normal.

RESULTS

We recorded Doppler signals in the left anterior descending coronary artery of 83 patients (78%). Significant stenosis of the left anterior descending coronary artery was observed in 24 out of 83 patients (29%). The prevalence of significant stenosis was higher (62 vs 29%; p = 0.006) in patients in which no Doppler signal was detected. The sensitivity, specificity, and accuracy of abnormal coronary flow reserve in detecting significant stenosis of the left anterior descending coronary artery were 87, 74 and 78%, respectively.

CONCLUSIONS

The measurement of coronary flow reserve by transthoracic Doppler echocardiography using a high-frequency transducer and echo-contrast agent is a feasible, widely available, and accurate method for detecting significant stenosis of the left anterior descending coronary artery.

Simultaneous analysis of wall motion and coronary flow reserve of the left anterior descending coronary artery by transthoracic doppler echocardiography during dipyridamole stress echocardiography

BACKGROUND

Coronary flow reserve (CFR) can be measured in the left anterior descending artery (LAD) by dipyridamole transthoracic Doppler echocardiography (DTTDE). This information may critically improve the diagnostic accuracy of dipyridamole stress echocardiography, which is limited by moderate sensitivity.

OBJECTIVE

We sought to assess the feasibility and accuracy of value of DTTDE.

METHODS

We evaluated 752 consecutive patients (478 men; mean age, 64.7 years) referred for dipyridamole stress echocardiography. The diastolic velocity in the LAD was continuously monitored with pulsed Doppler at baseline and during hyperemia induced by the infusion of 0.84 mg/kg of dipyridamole. CFR was calculated as the ratio of maximal and basal diastolic velocity; a value < 2 was considered to indicate decreased CFR. Wall motion was assessed semiquantitatively. Coronary angiography was performed in 132 patients the week after DTTDE.

RESULTS

Adequate tracings were obtained in 95% of patients studied (715 of 752). In the subset of 132 patients undergoing coronary angiography, 71 patients (group A) showed a nonsignificant (<70%) and 61 patients (group B) a significant stenosis of the LAD. In group A, 65 had a normal wall-motion response (91.5% specificity) and 19 patients showed a decreased CFR (73.2% specificity; P =.1). In group B, new wall-motion abnormalities were seen in 42 patients (68.8% sensitivity), whereas CFR was decreased in 52 patients (86.8% sensitivity; P <.02).

CONCLUSION

Simultaneous assessment of wall motion and CFR of the LAD with DTTDE was highly feasible and safe. The information about CFR had a significantly higher sensitivity than the analysis of wall motion during dipyridamole stress echocardiography.

Which is the better method in detecting significant left anterior descending coronary artery stenosis during contrast-enhanced dobutamine stress echocardiography: coronary flow velocity reserve or wall-motion assessment?

The diagnostic accuracy of dobutamine stress echocardiography (DSE) depends on wall-motion assessment. Coronary flow velocity reserve (CFVR) during DSE can be measured by transthoracic Doppler echocardiography. To investigate comparative diagnostic accuracy between wall-motion and CFVR assessment in the detection of significant left anterior descending coronary artery (LAD) stenosis, 274 patients underwent both contrast-enhanced DSE and coronary angiography. Intravenous contrast agent, Levovist, was injected to enhance left ventricular endocardial border delineation and coronary flow velocity in the LAD. Wall motion was assessed by standard technique, and CFVR was calculated as coronary flow velocity at peak dobutamine stress divided by baseline coronary flow velocity by transthoracic Doppler echocardiography. CFVR could be successfully obtained in 232 patients (feasibility, 85%). After excluding 14 patients with isolated diagonal stenosis, CFVR was significantly lower in 65 patients with significant LAD stenosis than it was in 153 patients without stenosis (1.62 +/- 0.56 vs 2.72 +/- 0.94, P <.001). CFVR < or = 2.0 had a 75% sensitivity, a 81% specificity, and a 79% diagnostic accuracy for detecting significant LAD stenosis, and these values were comparable with those by wall-motion analysis (sensitivity, 78%; specificity, 89%; and diagnostic accuracy, 86%). The measurement of CFVR in the LAD during DSE was feasible and the diagnostic accuracy of CFVR was equivalent to wall-motion assessment in the detection of LAD stenosis.

Assessment of intermediate stenosis in the left anterior descending coronary artery with contrast-enhanced transthoracic Doppler echocardiography

BACKGROUND

Visual or quantitative assessment of coronary angiography may not exactly predict the physiological significance of intermediate (40-70%) coronary stenosis. Coronary flow reserve is a well-established marker of the functional significance of coronary stenosis.

OBJECTIVES

The aim of this study was to compare the coronary flow velocity reserve (CFVR) using contrast-enhanced transthoracic Doppler echocardiography (CE-TTDE) with thallium-201 imaging in assessment of intermediate lesions in the left anterior descending coronary artery (LAD).

METHODS

A consecutive series of 50 patients with intermediate stenosis in the LAD underwent pharmacological stress thallium-201 imaging and CFVR measured by CE-TTDE.

RESULTS

CFVR could be measured in 49 of 50 patients by the present method. A CFVR <2.0 predicted the presence of a stress thallium defect in 12 of 14 patients (agreement=90%, kappa=0.76, P < 0.001). The sensitivity and specificity of CFVR for stress thallium-201 results were 86 and 91%, respectively. In contrast, significant stenosis (>50% by diameter) showed fair agreement for stress thallium defects (agreement=59%, kappa=0.28, P < 0.05).

CONCLUSIONS

In the evaluation of intermediate lesions in the LAD, CFVR as assessed by CE-TTDE could accurately predict the presence of ischemia on stress thallium imaging, whereas angiographic stenosis did not yield reliable results.

A guide to drug use during percutaneous coronary intervention

The past decade has seen major advances in adjunctive pharmacotherapy for percutaneous coronary intervention. Pharmacological therapeutic advances have resulted from a greater understanding of the pathophysiological mechanisms underlying platelet activation and aggregation, thrombin generation and thrombus formation. Specifically, refinements in the use of unfractionated heparin, developments in the use of low molecular weight heparins and direct antithrombin agents as well as improvement in both oral and parenteral adjunctive antiplatelet therapies have occurred and are reviewed herein.

Transthoracic Doppler echocardiography - noninvasive diagnostic window for coronary flow reserve assessment

This review focuses on transthoracic Doppler echocardiography as noninvasive method used to assess coronary flow reserve (CFR) in a wide spectrum of clinical settings. Transthoracic Doppler echocardiography is rapidly gaining appreciation as popular tool to measure CFR both in stenosed and normal epicardial coronary arteries (predominantly in left anterior descending coronary artery). Post-stenotic CFR measurement is helpful in: functional assessment of moderate stenosis, detection of significant or critical stenosis, monitoring of restenosis after revascularization. In the absence of stenosis in the epicardial coronary artery, decreased CFR enable to detect impaired microvascular vasodilatation in: reperfused myocardial infarct, arterial hypertension with or without left ventricular hypertrophy, diabetes mellitus, hypercholesterolemia, syndrome X, hypertrophic cardiomyopathy. In these diseases, noninvasive transthoracic Doppler echocardiography allows for serial CFR evaluations to explore the effect of various pharmacological therapies.

Angiographic assessment of coronary stenoses: a review of the techniques

This article reviews the fundamental techniques to quantify the physiological severity of (coronary) stenoses. Although a wide survey of different techniques and applications is provided, the focus of this review is on: 1) the assessment of the immediate effect of the stenoses on blood flow (i.e., the hemodynamic severity), and not on the assessment of the pathology of the vessel itself; 2) the flow reserve methods to defining the physiological severity of stenoses; and 3) the determination of blood flow and tissue perfusion by X-ray angiography (a short survey of other imaging modalities is provided as well). Although the practical implementation of the techniques is illustrated by applying them to coronary stenoses, most of the issues involved are of interest in other application areas (using other imaging modalities) as well. This review consists of four parts. The first part deals with the definition of stenoses severity; the second part with tracer kinetic theory necessary to determine flows by imaging; the third part focusses on (cardiac) imaging modalities, with an emphasis on X-ray angiography; and the last part illustrates the practical implementation of the techniques in cardiology.