Doppler and two-dimensional echocardiographic assessment of left ventricular function before and after intravenous dipyridamole stress testing for detection of coronary artery disease

Coronary collaterals provide a constant scaffold effect on the left ventricle and limit ischemic left ventricular dysfunction in humans

Coronary collaterals preserve left ventricular (LV) function during coronary occlusion by reducing myocardial ischemia and may directly influence LV compliance. We aimed to re-evaluate the relationship between coronary collaterals, measured quantitatively with a pressure wire, and simultaneously recorded LV contractility from conductance catheter data during percutaneous coronary intervention (PCI) in humans. Twenty-five patients with normal LV function awaiting PCI were recruited. Pressure-derived collateral flow index (CFI(p)): CFI(p) = (P(w) - P(v))/(P(a) - P(v)) was calculated from pressure distal to coronary balloon occlusion (P(w)), central venous pressure (P(v)), and aortic pressure (P(a)). CFI(p) was compared with the changes in simultaneously recorded LV end-diastolic pressure (ΔLVEDP), end-diastolic volume, maximum rate of rise in pressure (ΔLVdP/dt(max); systolic function), and time constant of isovolumic relaxation (ΔLV τ; diastolic function), measured by a LV cavity conductance catheter. Measurements were recorded at baseline and following a 1-min coronary occlusion and were duplicated after a 30-min recovery period. There was significant LV diastolic dysfunction following coronary occlusion (ΔLVEDP: +24.5%, P < 0.0001; and ΔLV τ: +20.0%, P < 0.0001), which inversely correlated with CFI(p) (ΔLVEDP vs. CFI(p): r = -0.54, P < 0.0001; ΔLV τ vs. CFI(p): r = -0.46, P = 0.0009). Subjects with fewer collaterals had lower LVEDP at baseline (r = 0.33, P = 0.02). CFI(p) was inversely related to the coronary stenosis pressure gradient at rest (r = -0.31, P = 0.03). Collaterals exert a direct hemodynamic effect on the ventricle and attenuate ischemic LV diastolic dysfunction during coronary occlusion. Vessels with lesions of greater hemodynamic significance have better collateral supply.

Lack of diastolic reserve in patients with heart failure and normal ejection fraction

BACKGROUND

The genesis of symptoms in patients with heart failure (HF) and normal ejection fraction (HFNEF) is unclear. Most investigations of HFNEF have focused on cardiac function at rest although most of these patients are breathless only on exercise. Stress-induced impairment in systolic or diastolic function could result in these symptoms. Method and Result- Forty-one patients with HFNEF and 29 controls underwent dobutamine stress echocardiography with color tissue Doppler imaging. Wall motion score index and regional myocardial systolic velocity (Sm) were measured at and peak stress. Systolic (Sa), early diastolic (Ea), and late diastolic (Aa) mitral annular velocities were averaged over the 6 periannular sites. Mitral annular long-axis velocity was lower in the HFNEF than controls at rest. Global, regional, and long-axis systolic function did not worsen with stress in the HFNEF group. The Ea decreased and the E/Ea increased with stress in the HFNEF but not in controls. The 6-minute walk distance was shorter and negatively correlated to the E/EA ratio at rest and stress in the HFNEF group.

CONCLUSIONS

Impaired diastolic reserve results in stress-induced increase in the left ventricular end-diastolic pressure in patients with HFNEF giving rise to exercise intolerance.

Role of Left Atrial Size in Risk Stratification and Prognosis of Patients Undergoing Stress Echocardiography

OBJECTIVES

The purpose of this study was to evaluate the role of diastolic dysfunction as measured by left atrial (LA) size in patients undergoing stress echocardiography (SE).

BACKGROUND

Left atrial size is a surrogate marker of diastolic function. However, its prognostic value in patients referred for SE is not well defined.

METHODS

We evaluated 2,705 patients (60 +/- 13 years, 47% men) undergoing SE (56% dobutamine). Patients with significant mitral valve disease (mitral stenosis or > or = moderate mitral regurgitation) were excluded. Enlarged LA was defined as a LA size indexed to body surface area > or =2.4 cm/m2. Follow-up (mean 2.7 +/- 1.0 years) for nonfatal myocardial infarction or cardiac death (n = 122) was obtained.

RESULTS

A dilated LA was able to further risk-stratify both the normal and abnormal SE groups. In the presence of a dilated LA, an abnormal SE portends a worse prognosis compared with patients with normal LA size. Cox proportional modeling showed that a dilated LA added incremental value over traditional risk factors, stress electrocardiographic, rest echocardiographic, and SE variables for the prediction of hard events (global chi-square increased from 90.4 to 113.1 to 176.1 to 184.4 to 190.5; p < 0.05 all groups). Left atrial size was a significant predictor of events independent of left ventricular systolic dysfunction and ischemia (relative risk = 1.84, 95% confidence interval 1.19 to 2.85; p = 0.006).

CONCLUSIONS

In patients referred for stress echocardiography, LA size provides independent and incremental value over standard risk factors including left ventricular systolic dysfunction and ischemia. Left atrial size is a powerful prognosticator and should be routinely used in the prognostic interpretation of stress echocardiography.

Vasodilator Stress Induces Infrequent Wall Thickening Abnormalities Compared to Perfusion Defects in Mild-to-Moderate Coronary Artery Disease: Implications for the Choice of Imaging Modality with Vasodilator Stress

BACKGROUND

Experimental evidence suggests that although vasodilator stress agents consistently induce regional flow disparity between stenosed and normal coronary vascular beds, the occurrence of functional myocardial ischemia is infrequent, especially in mild-to-moderate coronary artery stenosis. Thus, it is hypothesized that dipyridamole infusion, even at high doses, will result in a disproportionately higher frequency of perfusion defects compared to regional wall thickening abnormalities.

METHODS

We performed simultaneous high-dose (0.84 mg/kg) dipyridamole stress echocardiography (Echo) and Tc-99m sestamibi SPECT (MIBI, methoxyisobutyl isonitrile) in 46 patients with coronary artery diameter stenosis >50% and < o =90% in one or two epicardial coronary arteries, and no previous myocardial infarction.

RESULTS

Of a total of 828 segments, MIBI showed 97 reversible defects while Echo showed only 23 reversible wall thickening abnormalities. Of the 97 segments with reversible MIBI defects, only 13 (13%) showed simultaneous reversible wall thickening abnormalities during dipyridamole infusion. There were 24 patients with MIBI defects, of whom 10 (41%) showed a corresponding wall thickening abnormality. The sensitivity of MIBI and Echo for the detection of coronary artery disease was 52% and 21%, respectively (P = 0.001).

CONCLUSION

This suggests that vasodilator stress is not optimally suited for use with techniques that use regional wall thickening abnormality as a marker of ischemia for the diagnosis of coronary artery disease.

Use of pharmaceuticals in noninvasive cardiovascular diagnosis

A number of pharmaceuticals are employed as diagnostic agents for cardiovascular diseases. Four groups of agents are reviewed here: 1) vasoactive substances employed as adjuncts to physical maneuvers in diagnosis of structural heart disease; 2) vasodilators used to produce heterogeneity of coronary flow; 3) sympathomimetic agents simulating the effects of exercise on the heart for the purpose of detection of coronary artery stenosis; and 4) ultrasonic contrast agents used to enhance myocardial imaging for the assessment of segmental wall motion. In the first group are amyl nitrate, a vasodilator, and methoxamine and phenylephrine, both vasopressors. The vasodilators of the second group are dipyridamole and adenosine. When combined with scintigraphic perfusion imaging or with echocardiographic assessment of segmental wall motion, these agents can detect single- or multiple-vessel coronary artery disease with sensitivity and specificity comparable to submaximal exercise. They are especially useful for preoperative risk assessment before noncardiac surgery. The sympathomimetic agents of the third group, dobutamine and arbutamine, increase myocardial contractility and heart rate, and dilate the peripheral vasculature. As with the vasodilators, when combined with nuclear or echocardiographic techniques they are equivalent to exercise in detection of coronary disease. They are especially useful in patients with bronchospastic disease and for assessment of myocardial viability. Agents from groups 2 and 3 have acceptable side-effect and safety profiles. The last group reviewed includes echocardiographic contrast agents that, in this investigative setting, are employed to enhance detection of segmental wall motion when used with agents from groups 2 and 3.

Determinants of tissue Doppler measures of regional diastolic function during dobutamine stress echocardiography

BACKGROUND

Diastolic dysfunction induced by ischemia may alter transmitral blood flow, but this reflects global ventricular function, and pseudonormalization may occur with increased preload. Tissue Doppler may assess regional diastolic function and is relatively load-independent, but limited data exist regarding its application to stress testing. We sought to examine the stress response of regional diastolic parameters to dobutamine echocardiography (DbE).

METHODS

Sixty-three patients underwent study with DbE: 20 with low probability of coronary artery disease (CAD) and 43 with CAD who underwent angiography. A standard DbE protocol was used, and segments were categorized as ischemic, scar, or normal. Color tissue Doppler was acquired at baseline and peak stress, and waveforms in the basal and mid segments were used to measure early filling (Em), late filling (Am), and E deceleration time. Significant CAD was defined by stenoses >50% vessel diameter.

RESULTS

Diastolic parameters had limited feasibility because of merging of Em and Am waves at high heart rates and limited reproducibility. Nonetheless, compared with normal segments, segments subtended with significant stenoses showed a lower Em velocity at rest (6.2 +/- 2.6 cm/s vs 4.8 +/- 2.2 cm/s, P <.0001) and peak (7.5 +/- 4.2 cm/s vs 5.1 +/- 3.6 cm/s, P <.0001). Abnormal segments also showed a shorter E deceleration time (51 +/- 27 ms vs 41 +/- 27 ms, P =.0001) at base and peak. No changes were documented in Am. The same pattern was seen with segments identified as ischemic with wall motion score. However, in the absence of ischemia, segments of patients with left ventricular hypertrophy showed a lower Em velocity, with blunted Em responses to stress.

CONCLUSION

Regional diastolic function is sensitive to ischemia. However, a number of practical limitations limit the applicability of diastolic parameters for the quantification of stress echocardiography.

The comparable diagnostic accuracies of dobutamine-stress and dipyridamole-stress echocardiographies: a meta-analysis

BACKGROUND

Dobutamine-stress and dipyridamole-stress echocardiographies are widely used for pharmacological stress echocardiography, with wide geographical variations.

OBJECTIVE

To assess whether evidence derived from the literature indicates or disapproves that either stress modality confers diagnostic superiority.

METHODS

We performed a meta-analysis of peer-reviewed literature of published trials with head-to-head comparison, on the same population, of high-dose (0.84 mg/kg) dipyridamole-stress versus high-dose (up to 40 micrograms/kg per min) dobutamine-stress echocardiography. Data from 12 studies performed in 12 institutions in seven countries were analysed. Angiographic information about 818 patients was considered.

RESULTS

The diagnostic accuracies of the two tests were similar (631 of 818, 77%, for dipyridamole versus 654 of 818, 80%, for dobutamine, NS). Overall sensitivities were 403 of 568 (71%) for dipyridamole and 437 of 568 (77%) for dobutamine (P < 0.05). Sensitivities for patients with single-vessel disease were 177 of 275 (64%) for dipyridamole and 203 of 275 (74%) for dobutamine (P < 0.05). Sensitivities for patients with multivessel disease were 162 of 203 (80%) for dipyridamole and 163 of 203 (80%) for dobutamine (NS). Specificities were 232 of 250 (93%) for dipyridamole and 217 of 250 (87%) for dobutamine (P < 0.05). Data from an additional 26 studies with dipyridamole alone and 47 studies with dobutamine alone were analysed. The diagnostic accuracies were 80% for dipyridamole (n = 2038 patients; 95% confidence interval 75-82%) and 82% for dobutamine (n = 4264 patients; 95% confidence interval 79-84%).

CONCLUSION

High-dose dobutamine-stress and high-dose dipyridamole-stress echocardiographies have comparable diagnostic accuracies, with a slightly higher sensitivity with dobutamine and a slightly higher specificity with dipyridamole.

Myocardial infarction and remodeling in mice: effect of reperfusion

Anatomic and functional changes after either a permanent left anterior descending coronary artery occlusion (PO) or 2 h of occlusion followed by reperfusion (OR) in C57BL/6 mice were examined and compared with those in sham-operated mice. Both interventions generated infarcts comprising 30% of the left ventricle (LV) measured at 24 h and equivalent suppression of LV ejection velocity and filling velocity measured by Doppler ultrasound at 1 wk. Serial follow-up revealed that the ventricular ejection velocity and filling velocity returned to the levels of the sham-operated controls in the OR group at 2 wk and remained there; in contrast, PO animals continued to display suppression of both systolic and diastolic function. In contrast, ejection fractions of PO and OR animals were depressed equivalently (50% from sham-operated controls). Anatomic reconstruction of serial cross sections revealed that the percentage of the LV endocardial area overlying the ventricular scar (expansion ratio) was significantly larger in the PO group vs. the OR group (18 +/- 1.7% vs. 12 +/- 0.9%, P < 0.05). The septum that was never involved in the infarction had a significantly (P < 0.002) increased mass in PO animals (22.5 +/- 1.08 mg) vs. OR (17.8 +/- 1.10 mg) or sham control (14.8 +/- 0.99 mg) animals. Regression analysis demonstrated that the extent of septal hypertrophy correlated with LV expansion ratio. Thus late reperfusion appears to reduce the degree of infarct expansion even under circumstances in which it no longer can alter infarct size. We suggest that reperfusion promoted more effective ventricular repair, less infarct expansion, and significant recovery or preservation of ventricular function.

Dipyridamole stress echocardiography

Dipyridamole stress is the forerunner and prototype of pharmacological stress echo tests in the diagnosis of coronary artery disease. The safety of this test has been conclusively demonstrated as a result of extensive experience in large-scale multicenter projects. The diagnostic accuracy of dipyridamole stress echo is comparable to dobutamine and largely a function of the employed dose. Higher dosages (up to 0.84 mg/kg) are being required to achieve good sensitivity. The prognostic value has been shown to be independent and additive to clinical, exercise echocardiogram, and angiographic data. The test positive response should be titrated on the basis of severity, extent, and timing of induced dyssynergy with low positivity being associated to more anatomically and functionally severe forms of disease. Multicenter, randomized, prospective, international studies on cost-effectiveness directly comparing a noninvasive strategy centered on stress echo versus an invasive strategy centered on coronary angiography are currently ongoing.

Digital high frame rate stress echocardiography for detection of coronary artery stenosis by high dose dipyridamole stress testing

Diagnostic accuracy of high dose dipyridamole stress echocardiography (0.84 mg i.v./kg) for detecting coronary artery stenosis was assessed in 94 patients undergoing coronary angiography, and adverse effects were registered in the total study population of 120 patients. Echocardiographic analysis was performed with digital systolic cineloops with high frame-rate (47 frames/sec) for optimal left ventricular wall motion display. Results showed sensitivity of 73% for detection of arterial luminal stenosis > or = 75% or retrograde collateral flow to an occluded coronary artery. Sensitivity for detection of 1-vessel stenosis was 43% (6 of 14 patients), and for 2- and 3-vessel disease 79% (19 of 24) and 88% (16 of 18), respectively. Specificity was 92% (35 of 38), diagnostic accuracy 81%. The stenosed coronary artery was correctly localized in 85% of positive tests. Dipyridamole-induced increase in wall motion score index differed significantly between patients with 1-, 2-, and 3-vessel disease (0.02 +/- 0.17, 0.15 +/- 0.17, and 0.27 +/- 0.24, respectively), and early positive tests (dipyridamole dose of 0.56 mg/kg) were almost exclusively seen in patients with multivessel disease. Six patients (5%) developed symptomatic bradycardia and hypotension during the test. In conclusion, dipyridamole stress echocardiography is useful for detection and localization of coronary artery stenosis, particularly in patients with multivessel disease.

Doppler determined aortic acceleration after dipyridamole in the prediction of coronary artery disease

Change in the acceleration of aortic blood flow with stress testing is reported to reflect the presence of myocardial ischaemia. We studied its clinical usefulness when compared with dipyridamole thallium scintigraphy in 101 patients, of whom 64 had coronary angiography. Maximum aortic acceleration increased after dipyridamole (P < 0.0001), although no correlation existed between the aortic acceleration and evidence of thallium perfusion abnormalities. For the patients who had angiography, the increase in aortic acceleration was similar for those with no significant coronary stenoses, single vessel or multi-vessel disease. Compared with coronary angiography, Doppler measurement of maximum aortic acceleration had a sensitivity of 92% and a specificity of 37% for the detection of coronary artery disease. When patients with previous myocardial infarction or left ventricular dysfunction were excluded, there was still no relationship between the maximum aortic acceleration and the presence of coronary artery disease. We conclude that changes in the acceleration of aortic blood flow after dipyridamole stressing do not predict the presence or severity of coronary artery disease as measured from perfusion defects at thallium scintigraphy or by coronary angiography. We have observed a wide variability of aortic maximum acceleration in the evaluation of myocardial ischaemia, which we feel introduces serious limitations to its use in routine clinical practice.

Assessment of magnetic resonance velocity mapping of global ventricular function during dobutamine infusion in coronary artery disease

BACKGROUND

Magnetic resonance imaging (MRI) is a versatile technique for examination of the cardiovascular system but only recently has assessment of myocardial ischaemia in coronary artery disease (CAD) become possible, for example by demonstrating abnormalities of regional ventricular contraction during stress. Global ventricular function during stress was assessed by MRI of aortic flow, which has not been previously attempted.

DESIGN

Variables measured by MRI reflecting the effect of ischaemia on global ventricular function during dobutamine stress were correlated with thallium-201 myocardial perfusion tomography.

PATIENTS

10 normal controls and 25 patients with CAD.

SETTING

Tertiary cardiac referral centre.

METHODS

Novel MRI sequences and analysis systems were used to measure the following variables during staged dobutamine infusion to 20 micrograms/kg/min: stroke volume, cardiac output, cardiac power output, peak flow, peak flow acceleration, aortic back flow, and flow wave velocity. Heart rate, blood pressure, double product, and maximum tolerated dobutamine dose were also measured. Multiple regression analysis was used to compare changes during stress with 201TI tomography.

RESULTS

All parameters except for stroke volume and diastolic blood pressure increased in the controls. In the patients with CAD a significant relation was shown between the extent of reversible ischaemia and the change in peak flow acceleration (P < 0.00001), peak flow (P = 0.002), cardiac power output (P = 0.036), maximum dobutamine dose (P = 0.039), and systolic blood pressure (P = 0.04). Peak flow acceleration accounted for 58.4% of the variation in reversible ischaemia, and after allowing for this, only cardiac power output remained independently predictive adding a further 4.2% to the model (adjusted r2 = 0.626). A decrease in peak flow acceleration with an increase in dobutamine infusion indicated moderate or severe ischaemia (chi 2 = 10.2, P = 0.017).

CONCLUSION

MRI may be used to assess variables of aortic flow during stress, which includes acceleration with high temporal resolution. Peak flow acceleration was the most sensitive indicator of the effect of ischaemia on global ventricular function.

Coronary flow reserve assessment by dobutamine transesophageal Doppler echocardiography

OBJECTIVES

This study attempted to determine the sensitivity and specificity of coronary flow reserve derived using transesophageal echocardiography for left anterior descending coronary artery stenosis.

BACKGROUND

Transesophageal echocardiography can be used to measure coronary flow velocity and may provide a less invasive means of assessing coronary flow reserve.

METHODS

Seventy-eight adult patients were studied by pulsed Doppler transesophageal echocardiography of the proximal left anterior descending coronary artery during a control period and peak (i.e., 40 micrograms/kg body weight per min) dobutamine infusion. Coronary flow reserve index was calculated as the ratio of maximal diastolic coronary velocity at peak dobutamine infusion to the control level and was considered abnormal if < 1.81. Two-dimensional transesophageal left ventricular views were obtained for analysis of wall motion.

RESULTS

Coronary angiography showed > or = 70% (group A, n = 18), 0% to < 70% (group B, n = 21) and no (group C, n = 39) left anterior descending coronary artery diameter stenosis. An abnormal coronary flow reserve index did not differ from a new regional wall motion abnormality in sensitivity for left anterior descending coronary stenosis in group A (15 [83%] of 18 vs. 15 [83%] of 18, p = NS) but was significantly more sensitive in group B (12 [57%] of 21 vs. 2 [10%] of 21, p < 0.025). The specificity for no left anterior descending coronary stenosis in group C between a normal coronary flow reserve index and no new regional wall motion abnormality did not differ (87% vs. 97%, p = NS).

CONCLUSION

Doppler coronary flow reserve and two-dimensional dobutamine transesophageal echocardiography are equally sensitive for the detection of left anterior descending coronary stenosis > or = 70% and equally specific. However, Doppler coronary flow reserve, compared with two-dimensional dobutamine transesophageal echocardiography, is more sensitive for intermediate left anterior descending coronary stenosis and may play a significant adjunctive role to cardiac catheterization and other noninvasive techniques for assessing coronary artery disease.

Abnormal left ventricular early diastolic filling during dobutamine stress Doppler echocardiography is a sensitive indicator of significant coronary artery disease

OBJECTIVES

This study was designed to assess changes in Doppler indexes of left ventricular ejection and filling in response to high dose (40 micrograms/kg body weight per min) dobutamine stress and their utility in detection of coronary artery disease compared with that of new wall motion abnormalities.

METHODS

Ten patients with a low likelihood of coronary artery disease served as a control group, and 23 patients with documented single-vessel coronary artery disease underwent baseline and peak dobutamine echocardiographic and Doppler studies.

RESULTS

In both groups dobutamine induced similar increases in heart rate and systolic blood pressure. During the test, 14 patients had new wall motion abnormalities, 13 had angina, and 7 had electrocardiographic ST segment changes. No markers of ischemia occurred in the control subjects. Dobutamine induced qualitatively similar changes from baseline to peak dobutamine stress in control subjects and patients in peak aortic velocity (46% vs. 42%, p = NS), average aortic acceleration (61% vs. 43%, p = 0.03) and systolic time-velocity integral (7% vs. 2%, p = NS). Dobutamine caused marked increases in control subjects and decreases in patients in peak early filling velocity (E) (33% vs. -22%, p < 0.0001) and average E acceleration (76% vs. -28%, p < 0.0001). The response of Doppler early filling indexes to dobutamine stress was abnormal in all patients. There was no overlap in the percent change from baseline to peak dobutamine stress between control subjects and patients for E and E acceleration.

CONCLUSIONS

During dobutamine stress testing, an abnormal response of Doppler indexes of left ventricular early filling is a more sensitive marker of significant single-vessel coronary disease than are new wall motion abnormalities, and it is far superior to the response of Doppler ejection variables as a predictor of coronary artery disease.

Noninvasive study of left ventricular function and systemic haemodynamics during dipyridamole echocardiography stress test

Left ventricular function and systemic haemodynamics were noninvasively assessed during cardiac stress testing with dipyridamole (0.84 mg kg-1 i.v.) in 10 subjects (44-61 years) with normal coronary arteries (group 1), and in 14 patients (46-77 years) with coronary artery disease either without (group 2, n = 6) or with (group 3, n = 8) echocardiographic evidence for myocardial ischaemia during test. Left ventricular wall motion and dimensions, and aortic root pressure and flow were obtained by Doppler echocardiography combined with an externally traced subclavian artery pulse calibrated with brachial artery pressures. Peripheral arterial resistance, total arterial compliance, and aortic characteristic impedance were estimated from aortic root pressure and flow, by use of a three-element windkessel model of the systemic circulation. Left ventricular ejection fraction improved from baseline to peak stress in group 1 (mean +/- SD: 62 +/- 6% vs. 65 +/- 6%, P = 0.05), whereas it was not significantly changed in group 2 (58 +/- 10% vs. 56 +/- 6%) and decreased in group 3 (53 +/- 10% vs. 43 +/- 10%, P < 0.05). Otherwise, the haemodynamic response was similar in the three groups: heart rate and cardiac index increased by at least 30% and 37%, respectively, whereas stroke index and arterial pressures were maintained at or slightly above baseline. Peripheral resistance decreased by at least 22%, and total arterial compliance and aortic characteristic impedance were not significantly altered during test. The worsening of wall motion abnormality at peak stress in group 3 was not significantly related to the change in systemic haemodynamics. Thus, dipyridamole acted predominantly on the arterioles without significantly influencing the large systemic arteries. Myocardial ischaemia during test impaired regional and global left ventricular function, but did not influence the systemic haemodynamic response.

Dobutamine two-dimensional transesophageal echocardiographic stress testing for detection of coronary artery disease

Atrial pacing and dipyridamole transesophageal echocardiography have been shown to be sensitive and specific tests for the detection of coronary artery disease. However, the sensitivity and specificity of dobutamine transesophageal echocardiography have not been reported. The purpose of this study was to determine the feasibility, sensitivity, and specificity of dobutamine transesophageal echocardiography for the detection of coronary artery disease. Transesophageal echocardiographic assessment of left ventricular function was performed in 81 adult patients aged 62 +/- 12 years during stepwise infusion of dobutamine from 5.0 to 40 micrograms/kg/min. Ischemia was diagnosed by the development of severe hypokinesis, akinesis, or dyskinesis of a previously contractile left ventricular segment. Coronary artery disease was defined by angiography as a reduction in luminal diameter of > or = 70% of an epicardial or > or = 50% of the left main coronary artery. In patients who had undergone coronary artery bypass graft surgery, a stenotic bypass graft was defined as a reduction in luminal diameter of > or = 70%. In patients without previous CABG, significant coronary artery disease was present in 21 patients: 5 with single-vessel disease, 7 double-vessel disease, 8 triple-vessel disease, and 1 left main coronary disease. Dobutamine transesophageal echocardiography had a sensitivity of 90% (19 of 21) and specificity of 94% (49 of 52) for the detection of coronary artery disease. In patients with previous CABG (n = 8), the sensitivity and specificity for the detection of bypass graft stenosis were 100% (4 of 4) and 75% (3 of 4), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Dobutamine stress echocardiography: sensitivity, specificity, and predictive value for future cardiac events

We conducted a retrospective study to determine whether dobutamine stress echocardiography (DE) can be used for risk stratification of patients with known or suspected coronary artery disease (CAD). The study population consisted of 77 patients who underwent DE at our institution. The protocol consisted of an echocardiogram at baseline followed by imaging during intravenous dobutamine infusion starting at 10 micrograms/kg/min with increments of 10 micrograms/kg/min every 3 minutes to a maximum dose of 40 micrograms/kg/min. The reasons for performing DE included preoperative cardiac evaluation (30), chest pain (23), assessment of ischemia (18), and suspected restenosis (6). DE was classified according to wall motion response as normal (before and during DE), fixed abnormal (abnormal before with no change during DE), or ischemic (new wall-motion abnormality during DE). Mean duration of follow-up was 10 months. Cardiac events occurred in 14 patients. These included congestive heart failure in seven patients, myocardial infarction in six, and cardiac death in one. A normal wall-motion response (n = 40) was associated with a low incidence of cardiac events (5%), whereas 5 of 10 patients (50%) with an ischemic response had events. The risk of cardiac events was intermediate (26%) in patients with fixed abnormal wall motion. Overall sensitivity of DE for predicting future cardiac events was 85%. In 45 patients who underwent coronary angiography within 2 months of DE, the test detected CAD with a sensitivity of 71%. In conclusion, the wall-motion response during DE may be used for identifying patients at high risk for future cardiac events.

Dipyridamole-dobutamine echocardiography: a novel test for the detection of milder forms of coronary artery disease

OBJECTIVES

This study was designed to assess the clinical, hemodynamic and diagnostic effects of the addition of dobutamine to dipyridamole echocardiography.

BACKGROUND

Pharmacologic stress echocardiography with either dipyridamole or dobutamine has gained acceptance because of its safety, feasibility, diagnostic accuracy and prognostic power. The main limitation of the two tests is a less than ideal sensitivity in some patient subsets, such as those with limited coronary artery disease. We hypothesized that two pharmacologic stresses might act synergistically in the induction of ischemia by combining the mechanisms of inappropriate coronary vasodilation (with dipyridamole) and an increase in myocardial oxygen consumption (with dobutamine).

METHODS

One hundred fifty patients (mean [+/- SD] age 51 +/- 11 years) referred for stress echocardiography were initially studied by dipyridamole-dobutamine echocardiography. The test was stopped during the dipyridamole step in 95 patients for achievement of a predetermined end point (obvious dyssynergy induced by lower or higher dipyridamole dose), and dipyridamole-dobutamine tests were performed in 55 patients (negative dipyridamole echocardiographic test). In the same 150 patients the dobutamine echocardiographic test (up to 40 micrograms/kg body weight per min) was performed on a separate day.

RESULTS

Significant coronary artery disease (> 50% diameter stenosis of at least one major coronary vessel by quantitative coronary arteriography) was present in 131 patients (one vessel in 115; two vessels in 10, three vessels in 6), with normal coronary arteriography in 19. The feasibility of the dipyridamole-dobutamine test was 96%. Self-limiting side effects occurred in 5% of patients. The peak rate-pressure product was lowest during the dipyridamole test (132 +/- 30) and was comparable during the dobutamine (186 +/- 59) and dipyridamole-dobutamine tests (179 +/- 45, p = NS vs. dobutamine; p < 0.01 vs. dipyridamole). Sensitivity was 71% for dipyridamole, 75% for dobutamine and 92% for dipyridamole-dobutamine echocardiography (dipyridamole vs. dipyridamole-dobutamine, p < 0.01; dobutamine vs. dipyridamole-dobutamine, p < 0.01; dipyridamole vs. dobutamine, p = NS), whereas specificity was 89% for dipyridamole, 79% for dobutamine and 89% for dipyridamole-dobutamine echocardiography (p = NS for all).

CONCLUSIONS

Routine dobutamine addition to dipyridamole stress testing is clinically useful and well tolerated. It expands the spectrum of the disease detectable by pharmacologic stress echocardiography and allows documentation of milder forms of coronary artery disease that can be missed by conventional dipyridamole or dobutamine stress echocardiography.

Dipyridamole stress echocardiography in patients with severe left main coronary artery narrowing. Echo Persantine International Cooperative (EPIC) Study Group--Subproject "Left Main Detection"

From a population of 2,698 patients (579 evaluated early after an uncomplicated acute myocardial infarction) who underwent dipyridamole echocardiography testing (DET) and subsequent coronary angiography, left main (LM) stenosis > or = 50% was present in 73 (61 men and 12 women, mean age 62 +/- 8 years). These 73 patients were compared with a control group comprising 100 consecutive coronary patients without LM disease. Both groups were similar regarding mean age, sex, incidence of previous myocardial infarction, left ventricular function at rest, and severity of coronary artery disease by the number of diseased vessels excluding the LM. The proportion of patients receiving antianginal therapy during DET was higher in the LM than in the non-LM group (32 vs 14%; p < 0.01). No major complication (severe hypotension, sustained arrhythmia, myocardial infarction or death) occurred during DET. Of 73 patients with LM disease, 68 had positive DET (sensitivity 93%), dipyridamole time was 7.1 +/- 3.8 minutes, and the rest-peak stress variation in dipyridamole wall motion score index (1 = normal to 4 = dyskinesia, in an 11-segment model) was 0.37 +/- 0.23; 14 patients (19%) were resistant to aminophylline and needed nitrates to resolve ischemia. In the non-LM group, DET was positive in 72% (p < 0.001 vs LM), with a longer dipyridamole time (9.6 +/- 5.2 minutes; p < 0.001 vs LM), lower rest-peak stress wall motion score index variation (0.29 +/- 0.25; p < 0.05 vs LM), and less frequent antidote resistance (1%; p < 0.001 vs LM).(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnostic and prognostic value of dipyridamole echocardiography in patients with suspected coronary artery disease. Comparison with exercise electrocardiography

BACKGROUND

Before any new diagnostic test is accepted in clinical practice, such a test should be compared with established diagnostic tools in an appropriately large series of patients encompassing the complete spectrum of challenges to which the test is exposed. The aim of the present study was to assess the relative diagnostic and prognostic accuracies of high-dose dipyridamole echocardiography (two-dimensional echocardiographic monitoring during dipyridamole infusion up to 0.84 mg/kg over 10 hours) versus maximal symptom-limited bicycle exercise ECG test in patients with angina.

METHODS AND RESULTS

We studied 429 consecutive in-hospital patients who met the following inclusion criteria: history of chest pain, off antianginal therapy for at least 2 days (1 week for beta-blockers), no previous myocardial infarction and/or obvious regional left ventricular dyssynergy of contraction (akinesis or dyskinesis) at baseline, and acceptable acoustic window under resting conditions. All patients underwent dipyridamole echocardiography and exercise ECG--on different days and in random order--within 1 week of coronary angiography (which was performed independent of test results) and were followed up for 37.8 +/- 14 months (range, 1 to 73 months). Criteria of positivity were for dipyridamole echocardiography, a transient regional dyssynergy absent in the baseline examination; for exercise ECG, an ST-segment shift of > or = 0.1 mV from baseline; and for coronary angiography, a luminal reduction of > or = 75% in at least one major coronary vessel (50% for left main). There were 183 patients without and 246 with coronary artery disease; 132 had one-, 70 had two-, and 44 had three- and/or left main vessel disease. The specificity was higher for dipyridamole echocardiography than for exercise ECG (90% versus 51%, P < .001). The overall sensitivity of dipyridamole echocardiography was similar to that of exercise ECG (75% versus 74%, P = NS), with no significant differences in the subset with one- (67% versus 69%, P = NS), two- (79% versus 77%, P = NS), or three- (93% versus 86%, P = NS) vessel disease. During the follow-up, there were 20 deaths, 13 nonfatal myocardial infarctions, and 126 revascularization procedures. In the univariate analysis, dipyridamole resulted in higher chi 2 values than did exercise stress testing. A Cox forward stepwise survival analysis identified the dipyridamole time as the most powerful prognostic predictor of death (chi 2 = 19.4, P < .0001) of all invasive and noninvasive parameters. The dipyridamole time also provided independent and additional prognostic information when it was adjusted for age, diabetes, resting ECG, and exercise stress test according to a modified, interactive stepwise procedure. This is true when death only, death and myocardial infarction, and death, myocardial infarction, and revascularization procedures were considered end points.

CONCLUSIONS

In patients with no previous myocardial infarction and good resting left ventricular function, compared with exercise ECG, dipyridamole echocardiography has a similar sensitivity and a higher specificity for the noninvasive detection of angiographically assessed coronary artery disease. Dipyridamole echocardiography also provides information in addition to that provided by exercise ECG for predicting death, infarction, and all events when the presence as well as the timing, severity, and extension of dipyridamole-induced wall motion abnormalities are considered.

Effects of rider position on continuous wave Doppler responses to maximal cycle ergometry

Using 10 well-trained (VO2peak = 60.6 ml kg-1min-1) college age cyclists and continuous wave Doppler echocardiography, peak acceleration (PkA) and velocity (PkV) of blood flow in the ascending aorta, and the stroke velocity integral (SVI) were assessed to determine if rider position influenced the central haemodynamic responses to graded maximal cycle ergometry. Cyclist position was determined by hand placement on the uprights (UPRI) or drops (DROP) of conventional handlebars or using aerodynamic handlebars (AHB). All subjects consistently achieved a peak workload of 300 W. The Doppler variables did not differ significantly between rider positions at each stage of the maximal exercise tests but did change in response to increasing workloads. PkA was significantly (P < 0.05) greater at workloads > or = 240 W versus < or = 120 W. PkV increased significantly (P < 0.05) up to 180 W and then reached a plateau. SVI increased to a workload of 120 W and then progressively declined, becoming significantly (P < 0.05) less at 300 W. For each stage, neither submaximal VO2, VI nor heart rate (HR) differed significantly between each trial. These results suggest that rider position does not affect the physiological response to maximal bicycle ergometry as responses to each position are similar.

Assessment of anatomic and physiological severity of single-vessel coronary artery lesions by dipyridamole echocardiography. Comparison with positron emission tomography and quantitative arteriography

BACKGROUND

The aim of this study was to compare the results of dipyridamole-echocardiography test (DET: two-dimensional echo monitoring during dipyridamole infusion up to 0.84 mg/kg over a period of 10 minutes) with both anatomic and physiological parameters of coronary artery disease severity, assessed by computer-assisted quantitative coronary arteriography, and regional coronary flow reserve, measured by [13N]ammonia (13NH3) and dynamic positron emission tomography (PET), respectively.

METHODS AND RESULTS

We studied 31 patients with a history of chest pain and neither previous myocardial infarction nor resting wall motion abnormalities. Eighteen patients had single-vessel disease (> 50% stenosis of one major coronary vessel), and 13 had normal coronary arteries. The criterion for DET positivity was the appearance of a new transient regional wall motion abnormality. In patients with a positive DET, two parameters were evaluated: the dipyridamole time (ie, the time from the beginning of drug infusion to the development of obvious dyssynergy) and the wall motion score index (WMSI, a semiquantitative integrated estimation of extent and severity of the stress-induced dyssynergy). WMSI was derived by summation of individual segment scores divided by the number of segments interpreted. Quantification of regional myocardial blood flow was obtained by PET measurements of 13NH3 arterial input function and left ventricular myocardial tissue concentration both at control and after dipyridamole (0.56 mg/kg over 4 minutes). Maximal regional blood flow after dipyridamole in the region supplied by the stenotic vessel was significantly lower in the 11 patients with coronary artery disease and positive DET than in the 7 patients with coronary artery disease and negative DET (1.08 +/- 0.33 versus 1.98 +/- 0.37 mL.min-1.g-1, P < .01). In patients with a positive DET, regional coronary flow reserve correlated well with dipyridamole time (r = .87, P < .01) but not with peak WMSI (r = .25, P = NS). Patients with dipyridamole-induced akinesia or dyskinesia (n = 6) had a greater reduction in regional coronary flow reserve than did those showing hypokinesia (n = 5): 1.38 +/- 0.51 versus 2.17 +/- 0.42, P < .05. Percent area reduction was more severe in patients with DET positivity than in those with DET negativity (93.7 +/- 8.7% versus 77 +/- 10.3%, P < .01), and it correlated with regional coronary flow reserve (r = .64, P < .01) and dipyridamole time (r = -.59, P < .01).

CONCLUSIONS

In patients with single-vessel disease, DET shows an excellent specificity but a limited sensitivity; in these patients, DET positivity is associated with a physiologically important coronary stenosis. Severity of the anatomic stenosis and impairment in regional flow reserve are greater when the dipyridamole-induced dyssynergy appears earlier during the test. Therefore, a stratification of the anatomo-physiological severity of coronary artery disease can be obtained with DET, based mainly on the temporal allocation of the transient dyssynergy.

Safety of intravenous high-dose dipyridamole echocardiography. The Echo-Persantine International Cooperative Study Group

Clinical data on 10,451 high-dose (up to 0.84 mg/kg over 10 minutes) dipyridamole-echocardiography tests (DET) performed in 9,122 patients were prospectively collected from 33 echocardiographic laboratories, each contributing greater than 100 tests. All patients were studied for documented or suspected coronary artery disease (1,117 early [less than 18 days] after acute myocardial infarction and 293 had unstable angina). Significant side effects including major adverse reactions and minor but limiting side effects occurred in 113 patients (1.2%). Major adverse reactions occurred in 7 cases (0.07%). In 6 of these cases, adverse reactions were associated with echocardiographically assessed ischemia and included 1 prolonged cardiac asystole (complicated by acute myocardial infarction and coma, with death after 23 days), 1 short-lasting cardiac asystole, 2 myocardial infarctions, 1 pulmonary edema and 1 sustained ventricular tachycardia. In all 6 cases, the cardiologist-echocardiographer performing the study had a limited experience (less than 100 tests) with DET, and at off-line reading in 5 cases, the obvious echo-positivity preceded the onset of complications by 1 to 5 minutes. The only ischemia-independent major side effect was a short-lasting cardiac asystole that was reversed by aminophylline and atropine. Significant side effects associated with echocardiographically assessed ischemia occurred in 89 additional cases (21 with and 68 without concomitant echocardiographically assessed myocardial ischemia). The most frequent of these side effects was hypotension or bradycardia, or both, which occurred in 40 patients with negative and 6 with positive DET. In all cases, side effects promptly subsided after aminophylline. In 1,857 cases, the high dose was not given for echo-positivity before the eighth minute.(ABSTRACT TRUNCATED AT 250 WORDS)

Transesophageal dipyridamole echocardiography for diagnosis of coronary artery disease

The value of transthoracic dipyridamole echocardiography has been extensively documented. However, in some patients, because of a poor acoustic window, the rest transthoracic examination is not always feasible and the transesophageal approach is more convenient. Therefore, transesophageal echocardiography with high dose dipyridamole (up to 0.84 mg/kg body weight over 10 min) was performed in 32 patients in whom the transthoracic dipyridamole test either was not feasible (n = 29) or yielded ambiguous results (n = 3). The transesophageal echocardiographic test results were considered abnormal when new dipyridamole-induced regional wall motion abnormalities were observed. All 32 patients underwent coronary angiography; significant coronary artery disease was defined as greater than or equal to 70% lumen diameter narrowing in at least one major vessel. All patients also performed a bicycle exercise test 1 day before transesophageal dipyridamole echocardiography. Transesophageal stress studies were completed in all patients, with a maximal imaging time (in tests with a negative result) of 20 min. No side effects or intolerance to drug or transducer was observed. The left ventricle was always visualized in the four-chamber and transgastric short-axis views. High quality two-dimensional echocardiographic images were obtained in all patients both at rest and at peak dipyridamole infusion and were digitally analyzed in a quad-screen format. Coronary angiography showed coronary artery obstruction in 24 patients: 6 had single-, 9 double- and 9 triple-vessel disease. The transesophageal dipyridamole test showed a specificity of 100% and an overall sensitivity of 92%. The sensitivity of this test for single-, double- and triple-vessel disease was 67%, 100% and 100%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Stress Doppler echocardiography in the evaluation of ischemic heart disease

Doppler echocardiography enables convenient, noninvasive evaluation of global, systolic performance at rest and during exercise. Early studies suggested that Doppler parameters of systolic function were sensitive to exercise-induced myocardial ischemia and could identify patients with severe coronary artery disease. Subsequent investigation, however, has identified several factors in addition to myocardial ischemia that can significantly influence exercise Doppler study results. Thus, in order to obtain reliable information, the many factors that can influence Doppler measurements of aortic flow velocity and acceleration must be accounted for. Further work in this area is likely to produce results that encourage greater application of this technique in experimental and clinical research. At present, the role of stress Doppler echocardiography in the evaluation of ischemic heart disease remains uncertain.

Stress echocardiographic techniques. An overview

The choice of upright or supine exercise, pharmacological agents, or atrial pacing for the induction of ischemia depends on the goals and the imaging modality. Dynamic stress echocardiography has improved diagnostic accuracy over and above the stress electrocardiogram. Indications include patients with atypical symptoms, prior nondiagnostic stress electrocardiograms, or baseline electrocardiographic abnormalities. Pharmacological agents coupled with echocardiography do well in the high-risk preoperative patient (e.g., abdominal aneurysmectomy) or in those unable to walk due to orthopedic, neurological, or peripheral vascular disease. When there is uncertainty as to the physiological significance of anatomical (angiographic) stenosis, dynamic stress echocardiography in the ambulatory patient or atrial pacing (or beta-agonist pharmacological stressors) in the catheterization laboratory are useful. The accuracy of stress echocardiography for detection of ischemia in the follow-up of interventional procedures or for postmyocardial infarction risk stratification is superior to standard stress electrocardiography alone.

Dipyridamole echocardiography

Intravenous dipyridamole is a potent coronary vasodilator that has been extensively investigated over the past several years in the noninvasive assessment of patients with suspected coronary artery disease when exercise cannot be performed or is suboptimal. As an alternative to exercise studies, dipyridamole has been used in combination with different cardiac imaging techniques such as echocardiography, thallium scintigraphy, and radionuclide ventriculography. Extensive experience has been obtained with dipyridamole thallium-201 imaging for coronary artery disease screening, risk stratification, and prognosis after an acute coronary event. However, experience with the use of dipyridamole in combination with two-dimensional echocardiography has been limited. Dipyridamole increases coronary blood flow in nondiseased coronary vessels relative to coronary vessels with significant luminal narrowings. These provide the basis for detecting regional differences in flow by using different cardiac imaging techniques. Two-dimensional echocardiography would show regional wall-motion abnormalities in response to those regional differences in coronary blood flow. In this article, the most commonly used protocols, safety, and practicability of dipyridamole echocardiography are reviewed. As an alternative to exercise, dipyridamole echocardiography shares all the indications of a standard exercise test. Clinical applications of dipyridamole echocardiography include coronary artery disease screening, suspected coronary artery spasm, postmyocardial infarction risk stratification, evaluation of percutaneous transluminal coronary angioplasty results, and prognosis following an acute coronary event. Compared to conventional (ECG) exercise testing, dipyridamole echocardiography appears to be equally sensitive but more specific. Compared to atrial pacing, dipyridamole provokes ischemia at a lower rate pressure product and results in a greater ST segment depression suggesting that dipyridamole induces more profound myocardial ischemia than atrial pacing. Dipyridamole thallium and exercise thallium have shown to be equally sensitive and specific in the assessment of coronary artery disease. High dose dipyridamole echocardiography appeared to be equally sensitive and more specific. Experimental studies have demonstrated that dobutamine appears to be a more powerful pharmacological agent in inducing wall-motion abnormalities. Dipyridamole echocardiography as compared to stress echocardiography offers the advantage of obtaining better quality postintervention images. With regard to sensitivity and for coronary artery disease diagnosis, both techniques appear to render similar results. Although further studies are needed, the available data indicates that cardiac ultrasound imaging prior to and following the intravenous administration of dipyridamole may be an attractive alternative to thallium perfusion imaging in the clinical setting, particularly when radionuclide capabilities are not present.

Diagnosis of ischemic heart disease with adenosine echocardiography

To assess the feasibility, safety and diagnostic accuracy of adenosine infusion combined with echocardiography, 73 patients with suspected or known coronary artery disease underwent echocardiography at baseline and during a maximal intravenous adenosine infusion of 140 micrograms/kg per min. Compared with baseline values, adenosine caused an increase in heart rate, a decrease in systolic and diastolic blood pressure and a slight but significant increase in rate-pressure product. The echocardiographic images were digitized and randomly assigned in a quad-screen format for nonbiased interpretation. An ischemic response, defined as a new or worsening wall motion abnormality, developed in 25 patients; a fixed wall motion abnormality was present in 27 and no abnormality in 21. All patients underwent coronary angiography. The sensitivity of adenosine echocardiography for greater than or equal to 75% coronary artery diameter stenosis was 85% (46 of 54), with a specificity of 92% in patients with normal coronary arteries. In the 35 patients with a normal baseline electrocardiogram the sensitivity was 60%; 9 (82%) of 11 patients with multivessel disease were correctly identified. The sensitivity for adenosine electrocardiography (greater than or equal to 1-mm ST depression) was 35% with a specificity of 100%. Side effects were transient and mild; aminophylline was used in two patients. Thus, ischemic changes can be induced in patients with coronary artery disease with intravenous adenosine that, combined with echocardiography, is sensitive for the assessment of ischemic heart disease, particularly in patients with multivessel disease.

Prediction of major cardiac events after peripheral vascular surgery using dipyridamole echocardiography

Patients undergoing peripheral vascular surgery are at increased risk of postoperative cardiac complications. To evaluate the role of dipyridamole echocardiography in predicting major cardiac events, 109 unselected patients undergoing elective peripheral vascular surgery were prospectively studied. Preoperative dipyridamole echocardiograms were interpreted by an echocardiographer unaware of all clinical data. Patients were followed up until hospital discharge by research physicians without knowledge of dipyridamole echocardiography results. Outcomes were classified using strict predefined criteria by reviewers unaware of other clinical and echocardiographic data. Of the 109 patients, 9 (8%) had positive studies defined as development of new regional wall motion abnormalities or worsening of preexistent wall motion abnormalities. Of these 9 patients, 7 had postoperative events, including 3 cardiac deaths, 1 nonfatal myocardial infarction, 2 with unstable angina, and 1 with pulmonary edema. Only 1 event occurred among the 100 patients with negative studies. The sensitivity and specificity of dipyridamole echocardiography for predicting cardiac events after vascular surgery were 88 and 98%, respectively; the positive and negative predictive values were 78 and 99%. The relative risk of having a cardiac event if dipyridamole echocardiography was abnormal was 78 (95% confidence interval, 11 to 564; p less than 0.0001). If these results are extended and confirmed by other investigators, preoperative dipyridamole echocardiography may be an important screening test for patients undergoing elective peripheral vascular surgery.

Evaluation of dipyridamole-Doppler echocardiography for detection of myocardial ischemia and coronary artery disease

Doppler assessment of left ventricular filling and ejection during dipyridamole stress may supplement wall motion analysis for detection of myocardial ischemia and coronary artery disease (CAD). Thirty-four patients taking no cardioactive therapy were studied using intravenous dipyridamole (0.6 mg/kg) during 2-dimensional and pulsed Doppler echocardiography. Twelve patients had normal coronary arteries (group 1) and the remainder, who had significant CAD, were divided into groups 2 (n = 11) and 3 (n = 11). Only subjects in group 2 developed myocardial ischemia manifest as reversible regional asynergy and ST-segment depression. Heart rate increased (16 +/- 9 beats/min, p less than 0.01) and mean blood pressure decreased (-5 +/- 8 mm Hg, p = not significant) uniformly across groups. Exaggerated hyperkinesia of normally contracting wall segments was the common response to dipyridamole infusion in patients with CAD. The respective mean percent changes in peak early diastolic velocity, peak atrial velocity, their ratio and ejection peak velocity, and mean acceleration for groups 1 (20, 42, -13, 20 and 23%), 2 (22, 32, -2, 10 and 14%) and 3 (23, 33, -6, 16 and 18%) were similar. Comparisons between normal patients and those with CAD and between groups 2 and 3 revealed no significant differences in the effect of dipyridamole on any variable. However, a decrease in both peak velocity and mean acceleration of left ventricular ejection was seen in 3 of 4 group 2 patients who developed severe ischemia. Dipyridamole-Doppler echocardiography is insensitive for detection of CAD and appears unable to identify myocardial ischemia unless this is severe. Hemodynamic changes and compensatory wall motion induced by dipyridamole may explain these findings.

Pathophysiology of isolated systolic hypertension in elderly patients: Doppler echocardiographic insights

Systemic hemodynamics were evaluated with aortic pulsed wave Doppler echocardiography in 79 elderly subjects with isolated systolic hypertension participating in the Systolic Hypertension in the Elderly Program (SHEP) and were compared with the values in 39 normal age-matched subjects. Cardiac output was elevated (4.50 +/- 1.13 L/min versus 3.94 +/- 1.12 L/min, p less than 0.05) in patients with isolated systolic hypertension in comparison with values in normal elderly subjects. Systemic vascular resistance did not differ between both groups (2140 +/- 536 dyn.sec/cm-5 versus 2011 +/- 553 dyn.sec/cm-5, p = NS). The mean acceleration of blood during left ventricular ejection was similar in patients with isolated systolic hypertension in comparison with normals (12.6 +/- 5.6 m/sec2 versus 11.5 +/- 3.5 m/sec2, p = NS). Patients with isolated systolic hypertension had significantly decreased arterial compliance, as measured by the stroke volume-to-pulse pressure ratio (0.77 +/- 0.26 cm3/mm Hg versus 1.11 +/- 0.30 cm3/mm Hg, p less than 0.0001). The prevalence of aortic and mitral regurgitation as well as valvular and annular calcification did not differ between analyzed groups. Isolated systolic hypertension in elderly patients appears to be multifactorial, with reduced arterial compliance and increased cardiac output both playing a role.

Use of adenosine echocardiography for diagnosis of coronary artery disease

Two-dimensional echocardiography combined with exercise is sensitive and specific in the detection of coronary artery disease (CAD) by demonstrating transient abnormalities in wall motion. Frequently, however, patients cannot achieve maximal exercise because of various factors. Pharmacologic stress testing with intravenous adenosine was evaluated as a means of detecting CAD in a noninvasive manner. Patients with suspected CAD underwent echocardiographic imaging and simultaneous thallium 201 single-photon emission computed tomography during the intravenous administration of 140 micrograms/kg/min of adenosine. An increase in heart rate, decrease in blood pressure, and increase in double product were observed during adenosine administration. Initial observations revealed that wall motion abnormalities were induced by adenosine in areas of perfusion defects. The adenosine infusion was well tolerated, and symptoms disappeared within 1 to 2 minutes after termination of the infusion. Therefore preliminary observations suggest that adenosine echocardiography appears to be useful in the assessment of CAD.

Two-dimensional Doppler echocardiographic correlation of dipyridamole-thallium stress testing with isometric handgrip

To determine how frequently new wall-motion abnormalities that are indicative of ischemia accompany thallium redistribution, 47 consecutive patients underwent two-dimensional echocardiography during routine dipyridamole-thallium stress testing. A secondary aim of the study was to determine whether the addition of isometric handgrip exercises to the standard dipyridamole imaging protocol increased the frequency of wall-motion abnormalities or thallium redistribution. Echocardiograms and thallium scans were independently interpreted, and wall-motion abnormalities that appeared with dipyridamole, handgrip exercise, or both were compared with results of thallium imaging. Five of 24 patients with thallium redistribution had new wall-motion abnormalities, and the extent (number of segments) of thallium redistribution in these five patients was significantly greater than in those who did not have well-motion abnormalities (p less than 0.03). The addition of isometric handgrip exercises to the imaging protocol did not distinguish between patients with and without new wall-motion abnormalities or thallium redistribution. Thus new wall-motion abnormalities infrequently accompany thallium redistribution in routine dipyridamole stress testing in spite of the addition of handgrip exercises, but when new wall-motion abnormalities are present, they are associated with a greater area of thallium redistribution.

Functional significance of myocardial perfusion defects induced by dipyridamole using thallium-201 single-photon emission computed tomography and two-dimensional echocardiography

The mechanisms responsible for inhomogeneous myocardial blood flow after oral administration of a large dose (300 mg) of dipyridamole were assessed in 27 patients with serial thallium-201 single-photon emission computed tomography (SPECT) and simultaneous 2-dimensional echocardiograms. Myocardial tomographic images were obtained 50 minutes and 3 to 4 hours after administration of dipyridamole. Two-dimensional echocardiograms were recorded at baseline and then every 15 minutes for 60 minutes. Dipyridamole caused only a mild reduction in blood pressure (from 129 +/- 18 to 126 +/- 16 mm Hg) and a mild increase in heart rate (from 69 +/- 15 to 73 +/- 4 beats/min). Sixteen patients had perfusion defects after dipyridamole by SPECT, which underwent partial or total filling-in. Fourteen of these patients (87.5%) had either a new abnormality or further deterioration of a preexisting wall motion abnormality by 2-dimensional echocardiography, and thus were considered to have developed transient ischemia during dipyridamole administration. Ten of 11 patients (91%) with normal perfusion or fixed defects by SPECT had no further deterioration in wall motion after oral dipyridamole, and were thus considered to have no evidence of myocardial ischemia. In conclusion, most patients with transient thallium-201 defects after dipyridamole develop transient worsening of resting wall motion by 2-dimensional echocardiography, suggestive of true myocardial ischemia. Because myocardial oxygen demand, as indicated by the heart rate-blood pressure product, did not change significantly, the mechanism of myocardial ischemia in these patients is likely to be diminished regional blood flow related to a "subendocardial steal" induced by dipyridamole.

Usefulness of the dipyridamole-Doppler test for diagnosis of coronary artery disease

Two-dimensional and Doppler echocardiographic studies and a hemodynamic investigation were performed during dipyridamole testing in 42 subjects (13 control subjects and 29 patients with coronary artery disease [CAD]), to evaluate the ability of dipyridamole Doppler echocardiography in identifying patients with ischemic left ventricular dysfunction. In the control group, after dipyridamole infusion, Doppler-derived parameters increased significantly from baseline (p less than 0.001). In patients with CAD, peak flow velocity, flow velocity integral and stroke volume failed to increase after dipyridamole infusion (0.89 +/- 0.21 to 0.85 +/- 0.18 m/s, difference not significant; 14 +/- 3 to 12 +/- 4 cm, difference not significant, and 56 +/- 13 to 50 +/- 14 ml/beat, p less than 0.05, respectively). Heart rate, rate pressure product, systemic vascular resistance and mean right atrial pressure had similar variations in the 2 groups. Changes in the 3 Doppler-derived parameters are closely related to the variations of peak positive dP/dt, stroke volume (thermodilution) and left ventricular end-diastolic pressure and are closely related to the coronary angiography jeopardy score and to the appearance of wall motion abnormalities. Thus, by combining Doppler and 2-dimensional echocardiography, dipyridamole-induced myocardial ischemia may be detected in a high percentage of CAD patients, providing a sensitive tool for identifying patients with high-risk coronary artery anatomy.

Update on intravenous dipyridamole cardiac imaging in the assessment of ischemic heart disease

Intravenous dipyridamole is a relative selective coronary vasodilator which, when combined with thallium-201, provides a useful technique to assess myocardial perfusion. The intravenous dipyridamole is administered as an infusion at a rate of 0.14 mg/kg/min for 4 minutes. In the presence of significant coronary artery disease the increase of coronary blood flow is disproportionate between vessels with and without significant coronary lesions, providing the basis for detecting regional differences in flow using thallium-201. The test can be used alone or combined with low level exercise to increase test sensitivity. The test is safe when performed under medical supervision and when patient selection is done appropriately. Most of the side effects induced by dipyridamole infusion are well tolerated by patients and readily reversed with intravenous aminophylline and sublingual nitroglycerin. The average sensitivity and specificity of the dipyridamole thallium scintigraphy test from the major studies are 76% and 70%, respectively. The test is very useful in providing prognostic information in patients who are unable to exercise. A reversible thallium defect after dipyridamole infusion has been shown to be associated with significant mortality and morbidity in patients with documented or suspected coronary artery disease. The use of intravenous dipyridamole has been extended into other modalities of imaging, including 2-dimensional and Doppler echocardiography, to study functional changes in the left ventricular induced by the infusion of intravenous dipyridamole.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic importance of silent myocardial ischemia detected by intravenous dipyridamole thallium myocardial imaging in asymptomatic patients with coronary artery disease

One hundred seven asymptomatic patients who underwent intravenous dipyridamole thallium imaging were evaluated to determine prognostic indicators of subsequent cardiac events over an average follow-up period of 14 +/- 10 months. Univariate analysis of 18 clinical, scintigraphic and angiographic variables revealed that a reversible thallium defect, a combined fixed and reversible thallium defect, number of segmental thallium defects and extent of coronary artery disease were significant predictors of subsequent cardiac events. Of the 13 patients who died or had a nonfatal infarction, 12 had a reversible thallium defect. Stepwise logistic regression analysis selected a reversible thallium defect as the only significant predictor of cardiac events. When death or myocardial infarction was the outcome variable, a combined fixed and reversible thallium defect was the only predictor of outcome. In patients without previous myocardial infarction, the cardiac event rate was significantly greater in those with an abnormal versus normal thallium scan (55% versus 12%, p less than 0.001). Thus, intravenous dipyridamole thallium scintigraphy is a useful noninvasive test to risk stratify asymptomatic patients with coronary artery disease. A reversible thallium defect most likely indicates silent myocardial ischemia in a sizable fraction of patients in this clinical subset and is associated with an unfavorable prognosis.

Effect of blood pressure and afterload on Doppler echocardiographic measurements of left ventricular systolic function in normal subjects

Doppler echocardiographic measurements of blood flow velocity and acceleration in the ascending aorta have been shown to be useful descriptors of left ventricular (LV) systolic function. Few data exist, however, regarding the influence of loading conditions, particularly afterload, on these Doppler measurements in human subjects. Therefore, 14 normal volunteers (mean age 28 years) were studied using continuous wave Doppler echocardiography performed from the suprasternal notch both at baseline and during a controlled infusion of methoxamine. LV peak systolic (delta pk) and end-systolic (delta ES) wall stresses were calculated noninvasively using blood pressure and echocardiographic dimensions. Heart rate was kept constant by transesophageal atrial pacing. Methoxamine resulted in significant increases in mean systolic (163 +/- 8 vs 129 +/- 10 mm Hg) and diastolic (93 +/- 7 vs 71 +/- 12 mm Hg) blood pressure, as well as delta pk (277 +/- 25 vs 222 +/- 40 g/cm2 x 10(3] and delta ES (97 +/- 26 vs 77 +/- 19 g/cm2 x 10(3] (p less than or equal to 0.0004 for all). Conversely, peak velocity decreased from 0.91 +/- 0.18 m/s at baseline to 0.8 +/- 0.18 m/s (p less than or equal to 0.002) and peak acceleration decreased from 22 +/- 5 m/s2 at baseline to 19 +/- 5 m/s2 (p less than or equal to 0.006) during methoxamine infusion. Flow velocity integral and LV end-diastolic dimension remained unchanged. Thus, aortic flow velocity and peak acceleration are inversely related to afterload. This relation should be considered when using serial determinations of these Doppler parameters for patients in whom changing levels of afterload might occur.

Effects of left ventricular preload and afterload on ascending aortic blood velocity and acceleration in coronary artery disease

Doppler measurements of the velocity and acceleration of ascending aortic blood flow have been used as indexes of left ventricular (LV) contractility. Conflicting data exist, however, on the influence of LV loading conditions on these measurements. Therefore, simultaneous LV micromanometer pressure measurements, 2-dimensional echocardiography and continuous-wave Doppler studies were performed before and after preload or afterload manipulation in 16 patients with coronary artery disease. Nitroprusside (n = 9) was administered in combination with saline to maintain preload and achieve a 10 to 20% reduction in mean aortic pressure. Saline (n = 7) was administered (850 +/- 240 ml) to increase LV end-diastolic pressure 25 to 50%. All measurements were obtained during atrial pacing at a heart rate 10 to 15 beats/min above resting sinus rate. The administration of nitroprusside plus saline decreased LV end-systolic wall stress (94 +/- 27 to 67 +/- 14 g/cm2 X 10(3), p = 0.011) without changing LV end-diastolic pressure and end-diastolic dimension. Peak velocity (0.8 +/- 0.2 to 0.9 +/- 0.3, p = 0.044), velocity time integral (11 +/- 4 to 13 +/- 5 cm, p = 0.049) and mean acceleration (12 +/- 4 to 17 +/- 7 m/s2, p = 0.0014) increased significantly. The administration of saline alone significantly increased LV end-diastolic pressure (10 +/- 4 to 22 +/- 4 mm Hg, p = 0.0006), LV end-diastolic dimension (4.8 +/- 0.5 to 5.1 +/- 0.5 cm, p = 0.0001), peak velocity (0.9 +/- 0.3 to 1.0 +/- 0.4 m/s, p = 0.008), velocity-time integral (14 +/- 5 to 18 +/- 7 cm, p = 0.005), and mean acceleration (14 +/- 6 to 17 +/- 7 m/s2, p = 0.041). Thus, even a modest change in either preload or afterload altered peak velocity, the velocity time integral and mean acceleration. These data have important clinical implications regarding the application of Doppler aortic flow indexes in the assessment of LV function.

Nonexercise cardiac stress testing

Many patients who require evaluation for coronary artery disease are unable to undergo exercise stress testing because of physiologic or psychological limitations. Drs Vacek and Baldwin describe three alternative methods for assessment of cardiac function in these patients, all of which have high levels of diagnostic sensitivity and specificity.

Prognostic value of intravenous dipyridamole thallium scintigraphy after an acute myocardial ischemic event

Seventy-seven patients recovering from an acute coronary event were studied by intravenous dipyridamole thallium scintigraphy to evaluate the prognostic value and safety of the test in this patient subset. Forty-four patients (58%) had unstable angina and 33 (42%) had an acute myocardial infarction. One death occurred within 24 hours of testing. Sixty-eight patients were followed for an average of 12 months; 25, 31 and 23% had a fixed, reversible or combined thallium defect on their predischarge thallium scan. During follow-up, 10 patients died or had a nonfatal myocardial infarction; in each case, a reversible or combined myocardial thallium defect was present. Univariate analysis of 17 clinical, scintigraphic and angiographic variables showed that a reversible thallium defect and the angiographically determined extent of coronary artery disease were predictors of future cardiac events. The extent of coronary disease and global left ventricular ejection fraction were predictors of subsequent reinfarction or death. Logistic regression analyses revealed that a reversible thallium defect (p less than 0.001) and the extent of coronary disease (p less than 0.009) were the only significant predictors of a cardiac event. When death or reinfarction were the outcome variables, the extent of coronary disease (p less than 0.02) and left ventricular ejection fraction (p less than 0.06) were the only variables selected. Thus, intravenous dipyridamole thallium scintigraphy after an acute coronary ischemic syndrome is a useful and relatively safe noninvasive test to predict subsequent cardiac events.

Comparison of dipyridamole-Doppler echocardiography to thallium-201 imaging and quantitative coronary arteriography in the assessment of coronary artery disease

This study was undertaken to determine whether Doppler measurements of systolic aortic and diastolic mitral blood flow velocities could reliably detect the presence of reversible myocardial perfusion defects during intravenous dipyridamole-thallium-201 imaging. In addition, the ability of dipyridamole-Doppler echocardiography to predict the presence of significant coronary artery disease (CAD) was evaluated. Baseline and post-dipyridamole Doppler studies were performed in 10 normal control subjects and 23 patients with CAD. Aortic peak velocity and acceleration increased from baseline to post-dipyridamole in normal subjects by 0.07 +/- 0.07 m/s (p = 0.016) and 2.1 +/- 2.0 m/s2 (p = 0.009), respectively. The ratio of early to late peak transmitral velocities decreased slightly in normal subjects, by 0.18 +/- 0.72 (difference not significant), whereas the ratio of early to late transmitral velocity-time integrals increased by 0.07 +/- 0.93 (difference not significant). The response of aortic velocity and acceleration to intravenous dipyridamole was not significantly different between normal subjects, patients without reversible thallium-201 perfusion defects and patients with reversible thallium-201 perfusion defects. Furthermore, only 3 of 14 subjects with reversible thallium-201 perfusion defects had abnormal (greater than 2 standard deviations from the mean) responses of aortic velocity or acceleration to intravenous dipyridamole. No patient had an abnormal response of the early to late mitral peak velocity ratio. In addition, the response of Doppler aortic and mitral indexes to intravenous dipyridamole was not able to identify the presence of significant CAD as assessed by quantitative coronary arteriography.(ABSTRACT TRUNCATED AT 250 WORDS)