Effect of acute changes in heart rate on Doppler pulmonary artery acceleration time in a porcine model

Doppler measurements of pulmonary artery (PA) acceleration time (AT) have been used clinically to estimate PA pressure. However, these studies have been performed primarily in patients without tachycardia. To determine the effect of acute changes in heart rate on PA AT, atrial pacing studies were performed in seven closed-chest pigs. Pulsed Doppler PA flow velocity recordings were obtained from a parasternal position at pacing rates from 100 to 140 beats/min. PA pressure remained constant (mean +/- SD = 14 +/- 5 mm Hg) over the entire range of paced rates. When PA Doppler measurements were compared at heart rates of 100 and 140 beats/min, there were decreases at the higher heart rate in both acceleration time (110 +/- 12 vs 83 +/- 11 ms, p less than 0.01) and ejection time (ET) (315 +/- 23 vs 237 +/- 21 ms, p less than 0.01). In contrast, there was no change in either PA peak flow velocity (69 +/- 15 vs 62 +/- 18 cm/s) or the ratio of AT/ET (0.35 +/- .02 vs. .36 +/- .03). Consequently, when estimating PA pressure in states of tachycardia, the PA AT/ET ratio may be a more useful measurement than PA acceleration time.

Evaluation of age, gender, heart rate and blood pressure changes and exercise conditioning on Doppler measured aortic blood flow acceleration and velocity during upright treadmill testing

To evaluate the effect of upright exercise on aortic peak flow acceleration and velocity, 60 normal subjects between 15 and 74 years of age were evaluated by continuous wave Doppler during treadmill stress testing using the Bruce protocol. Subjects were divided into 3 age groups, each with 20 subjects: group 1, 21 +/- 4 years of age (mean +/- standard deviation), group 2, 36 +/- 5 years and group 3, 58 +/- 7 years. Periodic measurements of heart rate, blood pressure and Doppler blood flow velocity and acceleration were made before, during and after exercise. Continuous wave Doppler measurements were recorded from the suprasternal notch. The relation between Doppler aortic measurements and age, gender, normal heart rate and blood pressure responses during exercise, and exercise preconditioning, was evaluated. Age alone was significantly related (inversely) to immediate postexercise Doppler aortic peak blood flow peak acceleration (group 1, 55 +/- 15, group 2, 46 +/- 11 and group 3, 36 +/- 9 m/s2, p less than 0.05) and peak velocity (1.1 +/- 0.2, 1.0 +/- 0.2 and 0.8 +/- 0.2 m/s, respectively, p less than 0.01). Gender, heart rate and blood pressure changes during exercise, as well as preconditioning, had no significant effect on these flow characteristics. Consequently, the effects of normal aging must be considered when using Doppler measurements of peak aortic acceleration and velocity in the evaluation of left ventricular function, e.g., to detect or exclude the presence of coronary artery disease.

Refining the criteria for pulsed Doppler diagnosis of mitral regurgitation by comparison with left ventricular angiography

Doppler echocardiography is established as a useful method for detecting mitral regurgitation (MR). However, studies also show that Doppler echocardiography may be too sensitive for diagnosing pathologic MR. To determine whether the false-positive or clinically insignificant diagnosis of MR can be eliminated by defining more specific diagnostic criteria, pulsed Doppler findings were compared with left ventricular angiographic findings in 81 patients. Using the conventional Doppler criterion of any systolic increased spectral dispersion detected in the left atrium, sensitivity was 100% and specificity was 76%. Using holosystolic increased spectral dispersion as the criterion, sensitivity was 100% and specificity was 92%. Using the combined criteria of holosystolic increased spectral dispersion plus peak regurgitant blood flow velocity of greater than 150 cm/s, sensitivity was 100% and specificity was 97%. Doppler studies in 20 clinically normal persons showed that the combined Doppler criteria were 100% specific. In conclusion, the presence of holosystolic increased spectral dispersion within the left atrium with a peak regurgitant flow velocity greater than 150 cm/s appears to be as sensitive as and more specific than the presence of any systolic Doppler increased spectral dispersion in identifying patients with MR.

Evaluation of pulmonary artery pressure and resistance by pulsed Doppler echocardiography

Pulsed Doppler echocardiography was used to examine the relation between pulmonary valve motion and pulmonary artery (PA) flow velocity patterns in 39 adults. In 16 patients with normal PA pressure (mean pressure less than 20 mm Hg), PA flow velocity accelerated slowly to a peak flow velocity at midsystole (time to peak flow velocity, or acceleration time = 134 +/- 20 ms [mean +/- standard deviation]), followed by a slow deceleration to the end of ejection, producing a "dome-like" appearance. In contrast, in 23 patients with elevated PA pressure (mean pressure 20 mm Hg or more), flow velocity accelerated rapidly to a peak flow velocity in early systole (acceleration time = 88 +/- 25 ms, p less than 0.01), followed by rapid flow velocity deceleration to a nadir in midsystole. In 13 of these patients, a transient increase in flow velocity occurred in late systole, producing a "spike and dome" appearance. In patients with an acceleration time of 120 ms or less, there was a negative linear correlation with mean PA pressure, expressed by the equation: mean PA pressure = 90 - (0.62 X acceleration time). The standard error of the estimate was 8.3 mm Hg. A similar negative linear correlation was found between PA acceleration time and total pulmonary resistance. Using a PA acceleration time of 100 ms or less resulted in a 78% sensitivity and a 100% specificity for detection of elevated PA pressure. Although this Doppler method cannot precisely estimate PA pressure, it can be helpful in separating patients with normal pressure from those with elevated PA pressure.

Pulsed Doppler echocardiographic study of left ventricular filling in dilated cardiomyopathy

Patients with dilated cardiomyopathy (DC) have been reported to have abnormal left ventricular (LV) diastolic properties. To evaluate LV diastolic filling characteristics in patients with DC, pulsed Doppler echocardiography was used to study mitral flow velocity in 21 patients with DC and mitral regurgitation (MR), 12 patients with DC but no MR and 19 age-matched normal subjects. Diagnosis of MR was based on the Doppler echocardiographic finding of holosystolic turbulent flow in the left atrium. Peak mitral flow velocity in early diastole (PFVE) and during atrial systole (PFVA), PFVA/PFVE and deceleration half-time of early diastolic flow were measured from Doppler mitral flow velocity recordings. In 21 patients with DC and MR, PFVE (61 +/- 13 cm/s), PFVA (37 +/- 19 cm/s) and PFVA/PFVE (0.6 +/- 0.4) were not significantly different from PFVE (53 +/- 10 cm/s), PFVA (47 +/- 12 cm/s) and PFVA/PFVE (1.0 +/- 0.4) in normal subjects (p greater than 0.05). Deceleration half-time in DC patients with MR (62 +/- 32 ms) was shorter than normal (87 +/- 25 ms) (p less than 0.05). In contrast, PFVE (31 +/- 11 cm/s) was lower and PFVA/PFVE (1.7 +/- 0.8) was higher in the 12 DC patients without MR than in normal subjects and DC patients with MR (p less than 0.005). PFVA (46 +/- 8 cm/s) and deceleration half-time (88 +/- 33 ms) in patients without MR were not significantly different from normal mean values. Thus, abnormalities of peak diastolic mitral flow velocity were detected in DC patients without MR but not in DC patients with MR, suggesting that MR masks LV filling abnormalities in patients with DC.

Left ventricular filling in hypertrophic cardiomyopathy: a pulsed Doppler echocardiographic study

Abnormal left ventricular diastolic properties have been described in patients with hypertrophic cardiomyopathy. To evaluate the diastolic filling characteristics of the left ventricle in patients with this disease, pulsed Doppler echocardiography was used to study mitral flow velocity in 17 patients with hypertrophic cardiomyopathy (11 with and 6 without systolic anterior motion of the mitral valve) and 16 age-matched normal subjects. There were no statistically significant differences between patients with hypertrophic cardiomyopathy with and without systolic anterior motion with regard to ventricular septal thickness, left ventricular posterior wall thickness, left ventricular internal dimensions or the extent of hypertrophy evaluated by two-dimensional echocardiography. Mitral regurgitation was detected by Doppler echocardiography in all 11 patients with and in 2 (33%) of the 6 patients without systolic anterior motion of the mitral valve. Early and late diastolic peak flow velocity, the ratio of late to early diastolic peak flow velocity and deceleration of early diastolic flow were measured from Doppler mitral flow velocity recordings. There were no statistically significant differences in these four indexes between the patients with systolic anterior motion and normal subjects. In contrast, the patients with hypertrophic cardiomyopathy without systolic anterior motion showed lower early diastolic peak flow velocity, higher ratio of late to early diastolic peak flow velocity and lower deceleration of early diastolic flow compared with the patients with systolic anterior motion and normal subjects, suggesting impaired left ventricular diastolic filling.(ABSTRACT TRUNCATED AT 250 WORDS)

A simple Doppler echocardiographic method for estimating severity of aortic regurgitation

Doppler echocardiography is useful for detecting aortic regurgitation (AR). To determine if the presence of retrograde holodiastolic flow in the abdominal aorta can be used to assess the severity of AR, abdominal aortic flow velocity was examined by pulsed Doppler echocardiography in 33 patients with AR and 10 patients without AR confirmed by aortography, and in 15 normal subjects. Among the 33 patients with AR, 15 had mitral regurgitation, 11 had mitral stenosis, 8 had aortic stenosis, 5 had prosthetic mitral valves, 4 had prosthetic aortic valves and 2 had aorticopulmonary shunts. No retrograde holodiastolic flow was found in the abdominal aorta of 15 normal subjects or 10 patients without AR. Of the 22 patients with 1+ or 2+ AR independently determined by injection of iodinated contrast into the aortic root, 21 did not have retrograde holodiastolic abdominal aortic flow, whereas all 11 patients with 3+ or 4+ AR had retrograde holodiastolic flow in the abdominal aorta. One patient with 1+ AR and a left-to-right aorticopulmonary shunt had retrograde holodiastolic flow in the abdominal aorta. The finding of holodiastolic retrograde flow in the abdominal aorta is useful for distinguishing patients with severe AR from those with mild or absent AR. Moreover, the method is easy to perform and results appear to be independent of the presence of other cardiac diseases except significant aorticopulmonary shunt.

Studies of Doppler aortic flow velocity during supine bicycle exercise

Although Doppler echocardiography is useful in the assessment of left ventricular function at rest, little information is available on the application of this technique during exercise. Consequently, Doppler aortic flow studies were performed in 17 young normal subjects during and after supine bicycle exercise. The purposes of the study were to determine the feasibility of recording Doppler aortic flow velocity with a suprasternal notch transducer during exercise and to assess the changes in normal aortic flow velocity parameters during exercise and early recovery. Each subject exercised until fatigue; mean duration of exercise was 10 minutes. Heart rate increased from a mean of 69 beats/min at control to 159 beats/min at peak exercise. On average, aortic peak flow velocity increased by 45% from control, reaching its maximum at 2 minutes after exercise. Ejection time decreased by 34% during exercise, being shortest at peak exercise. Heart rate, peak flow velocity and ejection time had not returned to normal by 10 minutes after exercise. Aortic flow velocity integral (a relative measure of stroke volume) decreased by 10% at peak exercise (p less than 0.05) compared with control, but had returned to control at 2 minutes after exercise. Despite mild aliasing, increased spectral dispersion, faster heart rates and increased respiratory rate during maximal exercise, aortic flow velocity measurements could be recorded using the suprasternal technique. These baseline Doppler exercise data should be useful in further studies of exercise hemodynamic changes in patients with heart disease.

Superiority of two-dimensional measurement of aortic vessel diameter in Doppler echocardiographic estimates of left ventricular stroke volume

Attempts to measure left ventricular stroke volume utilizing the Doppler aortic flow method have found varying correlations between invasive thermodilution and non-invasive Doppler methods. Because stroke volume is the product of the Doppler flow velocity integral (that is, the area under the flow velocity curve) and the cross-sectional area of the vessel through which blood flows, both variables are potential sources of error. Previous studies have shown that the Doppler flow velocity integral can be measured with acceptable reproducibility in the ascending aorta. Consequently, in this study an attempt was made to determine empirically the optimal method for measuring aortic diameter and area. The diameter of the ascending aorta was measured utilizing four M-mode and seven two-dimensional echocardiographic conventions. Doppler aortic flow velocity patterns were recorded with a 2.25 MHz M-mode echocardiographic transducer from the suprasternal notch by mapping the ascending aorta until aortic peak flow velocity was recorded. In 19 adult patients undergoing cardiac catheterization for clinical indications, Doppler stroke volume estimates utilizing the various echocardiographic conventions for measuring aortic root diameter and area were compared with simultaneous measurements of stroke volume by the thermodilution technique. The best correlation (r = 0.87) with thermodilution stroke volume was obtained by estimating aortic area from the two-dimensional parasternal long-axis images with the aortic dimension measured distal to the aortic sinuses from the inner to inner wall. The data were related by the equation: Thermodilution stroke volume = (0.73) X (two-dimensional Doppler stroke volume) + 17 cc.(ABSTRACT TRUNCATED AT 250 WORDS)

Reproducibility of Doppler aortic blood flow measurements: studies on intraobserver, interobserver and day-to-day variability in normal subjects

Doppler aortic flow velocity measurements have been used to assess quantitatively left ventricular performance at rest and after pharmacologic and other hemodynamic interventions. To permit more meaningful interpretation of Doppler data, 10 normal subjects were studied to establish the intraobserver, interobserver and day-to-day variability in Doppler aortic flow velocity measurements. In each subject, pulsed Doppler recordings of ascending aortic flow velocity were obtained from the suprasternal notch on 2 different days (mean interval 6 days), with the same technician performing and same physician reading both Doppler studies to evaluate day-to-day variability of measurements. Interobserver variability was assessed by having 2 observers read each Doppler study. Both observers read the Doppler records from both days again at a second session to determine intraobserver variability. Intraobserver variability ranged from 1.9 +/- 1.8 to 3.2 +/- 2.9% for ejection time, peak flow velocity and flow velocity integral, but was higher for acceleration time (7.9 +/- 6.6%). Interobserver variability ranged from 3.5 +/- 2.2 to 5.4 + 3.4% for peak flow velocity, ejection time and flow velocity integral, but was notably higher for acceleration time (17 +/- 9%). Day-to-day variability was higher for acceleration time (7.0 +/- 5.2%) than for ejection time, peak flow velocity and flow velocity integral (range from 3.6 +/- 3.1 to 5.2 +/- 4.0%).(ABSTRACT TRUNCATED AT 250 WORDS)