Effect of heart rate on Doppler indexes of systolic function in humans

Left ventricular output indices in hospitalized heart failure: when "simpler" may not mean "better"

Assessment of left ventricular (LV) output in hospitalized patients with heart failure (HF) is important to determine prognosis. Although echocardiographic LV ejection fraction (EF) is generally used to this purpose, its prognostic value is limited. In this investigation LV-EF was compared with other echocardiographic per-beat measures of LV output, including non-indexed stroke volume (SV), SV index (SVI), stroke distance (SD), ejection time (ET), and flow rate (FR), to determine the best predictor of all-cause mortality in patients hospitalized with HF. A final cohort of 350 consecutive patients hospitalized with HF who underwent echocardiography during hospitalization was studied. At a median follow-up of 2.7 years, 163 patients died. Non-survivors at follow-up had lower SD, SVI and SV, but not ET, FR and LV-EF than survivors. At multivariate analysis, only age, systolic blood pressure, chronic kidney disease, chronic obstructive pulmonary disease, use of angiotensin-converting enzyme inhibitors/angiotensin receptor blockers and SVI remained significantly associated with outcome [HR for SVI 1.13 (1.04-1.22), P = 0.003]. In particular, for each 5 ml/m² decrease in SVI, a 13% increase in risk of mortality for any cause was observed. SVI is a powerful prognosticator in HF patients, better than other per-beat measures, which may be simpler but partial or incomplete descriptors of LV output. SVI, therefore, should be considered for the routine echocardiographic evaluation of patients hospitalized with HF to predict prognosis.

Ultrasound imaging velocimetry: effect of beam sweeping on velocity estimation

As an emerging flow-mapping tool that can penetrate deep into optically opaque media such as human tissue, ultrasound imaging velocimetry has promise in various clinical applications. Previous studies have shown that errors occur in velocity estimation, but the causes have not been well characterised. In this study, the error in velocity estimation resulting from ultrasound beam sweeping in image acquisition is quantitatively investigated. The effects on velocity estimation of the speed and direction of beam sweeping relative to those of the flow are studied through simulation and experiment. The results indicate that a relative error in velocity estimation of up to 20% can be expected. Correction methods to reduce the errors under steady flow conditions are proposed and evaluated. Errors in flow estimation under unsteady flow are discussed.

Effect of hormone replacement therapy on lipids and left ventricular function in postmenopausal smokers

OBJECTIVE

Menopause and smoking have negative effects on the cardiovascular system. The study was planned to investigate the influence of oral hormone replacement therapy (HRT) on heart function and lipids in postmenopausal smokers.

METHODS

Lipid levels and left ventricular systolic and diastolic function by means of echocardiography were assessed before entering the study and at 6-month intervals during the 12 months of oral HRT in 62 postmenopausal women, 30 of whom were smokers and 32 were non-smokers.

RESULTS

Oral HRT caused a significant decrease in levels of total cholesterol and low density lipoprotein (LDL) cholesterol and a significant increase in high density lipoprotein (HDL) cholesterol in non-smokers. This effect was not evident in smokers. Echocardiography revealed a significant improvement of systolic function (ejection fraction, left ventricular outflow tract velocity, forward velocity integral, acceleration time and mean systolic acceleration) and diastolic function (diastolic time, duration of the early filling phase, peak velocity of early mitral flow, and the ratio of late to early peak mitral flow) in non-smokers. In smokers, a significant increase in some parameters of systolic function (ejection fraction, acceleration time and mean systolic acceleration) and an insignificant change in diastolic function were observed. Oral HRT of 12 months' duration has very limited beneficial effects on

CONCLUSION

lipids and left ventricular heart function in postmenopausal women who smoke.

Usefulness of stroke distance by echocardiography as a surrogate marker of cardiac output that is independent of gender and size in a normal population

Left ventricular outflow tract stroke distance (SD) can be measured using pulsed-wave Doppler echocardiography, and is independent of body size. Moreover, persons with structurally normal hearts (heart rate < 55 beats/min) had SD > 0.18 m, and those with a heart rate > 95 beats/min had SD < 0.22 m; outside of these parameters, low- and high-output states are likely to exist, and suspicion of these can be confirmed by calculation of minute distance (normal range 9.7 to 20.5 m/min).

Effect of estrogen replacement therapy on cardiac function in postmenopausal women with and without flushes

Left ventricular heart function and its response to long-term estrogen replacement therapy was assessed in 30 postmenopausal women, 20 of whom had modest to severe hot flushes and 10 of whom had never had them. Continuous transdermal estradiol was given to women who had surgically induced menopause, and a combination of transdermal estradiol and sequential medroxyprogesterone acetate was given to those who had spontaneous menopause. Left ventricular systolic and diastolic function was evaluated by complete two-dimensional M-mode and pulsed Doppler echocardiography before and after 6 and 12 months of therapy. The parameters assessed were: systolic and diastolic blood pressure, heart rate, cardiac septal and posterior wall dimensions, left ventricular end-systolic and end-diastolic dimensions and volumes, ejection fraction (EF), ejection time, peak left ventricular outflow velocity (PFV), flow velocity integral (FVI), acceleration time (AT), mean acceleration of systolic flow (MA), duration of early and late filling phase, peak velocity of the early (E) and late (A) mitral flow, and A/E velocity ratio. Although no difference in chamber and wall dimensions between flushers and non-flushers was found, women with hot flushes had lower (not significantly) EF, PFV, FVI, MA, blood pressure and heart rate before therapy. Twelve-month estrogen replacement therapy significantly reduced cardiac wall dimensions and improved systolic function in both flushers and non-flushers. However, stroke volume, EF and MA were increased whereas systolic blood pressure and heart rate were decreased more in flushers. Also, the increase in E mitral flow and decrease in A/E were more pronounced in flushers. Thus, although estrogen replacement therapy significantly improves heart function in healthy postmenopausal women, there appears to be some minor differences in response between flushers and non-flushers.

Exercise echocardiography in postmenopausal hormone users with mild systemic hypertension

Rest and exercise echocardiography (at dynamic and isometric exercise) were performed in 30 postmenopausal women (aged 54 +/- 4 years) with borderline to mild hypertension. They were then divided into 2 groups: 17 women who started oral hormone replacement therapy (0.625 mg/day conjugated estrogens or 2 mg/day estradiol) and a control group of 13 nonusers. After 6 to 9 months, a second echocardiography was performed in 26 women (4 withdrew). There were only a few changes in values obtained in the 12 controls at the end of follow-up compared with baseline. Primarily, these changes included a slight decrease in systolic blood pressure at rest and on exercise. Several significant morphologic and hemodynamic alterations appeared in 14 hormone users. Left ventricular cavity dimensions and mass became smaller: mean end-diastolic diameter decreased from 45.9 +/- 3 mm at baseline to 44.4 +/- 3 mm at study termination (p = 0.007). The corresponding values for end-systolic diameter were 25.8 +/- 4 mm and 23.9 +/- 4 mm (p = 0.006); for left atrium diameter, it was 34.5 +/- 4 mm and 32.5 +/- 4 mm (p = 0.001); for left ventricular wall width, it was 19.9 +/- 2 mm and 19.3 +/- 2 mm (p = 0.02); for left ventricular mass, it was 197 +/- 28 g and 179 +/- 32 g (p = 0.006). The resting aortic blood flow velocity and acceleration increased: 119 +/- 18 cm/s before therapy versus 129 +/- 23 cm/s while on hormone substitution (p = 0.04), and 13.6 +/- 3 m/s2 versus 16.5 +/- 4 m/s2 (p = 0.008), respectively. Mean rest to peak exercise systolic blood pressure difference became smaller after hormones: 39 +/- 19 mm Hg versus 28 +/- 13 mm Hg (p = 0.03) during dynamic exercise, and 43 +/- 22 mm Hg versus 25 +/- 13 mm Hg (p = 0.004) during isometric exercise. The above data probably indicate that with hormone replacement therapy, there is an improvement in cardiac function both at rest and during exercise.

Effects of hypercapnia on hemodynamic, inotropic, lusitropic, and electrophysiologic indices in humans

STUDY OBJECTIVE

The inotropic, lusitropic, and electrophysiologic effects of acute hypercapnia in humans are not known. Although the effects of hypercapnia on the systemic circulation have been well documented, there is still some debate as to whether hypercapnia causes true pulmonary vasoconstriction in vivo. We have therefore evaluated the effects of acute hypercapnia on these cardiac indices and the interaction of hypercapnia with the systemic and pulmonary vascular beds in humans.

PARTICIPANTS AND INTERVENTIONS

Eight healthy male volunteers were studied using Doppler echocardiography. After resting for at least 30 min to achieve baseline hemodynamic parameters (T(0)), they were rendered hypercapnic to achieve an end-tidal carbon dioxide (CO2) of 7 kPa for 30 min by breathing a variable mixture of CO2/air (T1). They were restudied after 30 min recovery breathing air (T2). Hemodynamic, diastolic, and systolic flow parameters, QT dispersion (maximum-minimum QT interval measured in a 12-lead ECG), and venous blood samples for plasma renin activity (PRA), angiotensin II (ANG II), and aldosterone (ALDO) were measured at each time point.

RESULTS

Hypercapnia compared with placebo significantly increased mean pulmonary artery pressure 14 +/- 1 vs 9 +/- 1 mm Hg and pulmonary vascular resistance 171 +/- 17 vs 129 +/- 17 dyne.s.cm-5, respectively. Heart rate, stroke volume, cardiac output, and mean arterial BP were increased by hypercapnia. Indexes of systolic function, namely peak aortic velocity and aortic mean and peak acceleration, were unaffected by hypercapnia. Similarly, hypercapnia had no effect on lusitropic indexes reflected by its lack of effect on isovolumic relaxation time, mitral E-wave deceleration time, and mitral E/A wave ratio. Hypercapnia was found to significantly increase both QTc interval and QT dispersion: 428 +/- 8 vs 411 +/- 3 ms and 48 +/- 2 vs 33 +/- 4 ms, respectively. There was no significant effect of hypercapnia on PRA, ANG II, or ALDO.

CONCLUSION

Thus, acute hypercapnia appears to have no adverse inotropic or lusitropic effects on cardiac function, although repolarization abnormalities, reflected by an increase in QT dispersion, and its effects on pulmonary vasoconstriction may have important sequelae in man.

Quantitative Echoca rdiograpy Part III

A comprehensive two-dimensional echocardiographic examination provides useful information that is superior to MT-mode regarding left ventricular chamber sizes and systolic performance, including ejection fraction. Although we rely on visual estimates, quantitative measurements can be particularly valuable in patients with mild or moderate left ventricular systolic dysfunction. Measurements of left ventricular mass by two-dimensional echocardiography is supenror to Ml-mode to detect left ventricular hypertrophy. Two-dimensional echocardiography combined with pulsed Doppler echocardiography can be used to accurately measure stroke volume and to assess changes during medical therapy or after interventions. Future work is needed to assess the significance of continuous-wave Doppler-derived rate of pressure change in patients with mitral regurgitation.

Left ventricular systolic performance during acute hypoxemia

STUDY OBJECTIVE

Although some of the cardiovascular responses to hypoxemia are well described, effects on myocardial contractility have not been defined. Such effects are readily assessed by noninvasive techniques and we have therefore evaluated Doppler-phonocardiographic parameters of systolic left ventricular contractility in normal humans rendered hypoxemic.

DESIGN

Eight healthy male volunteers were studied. Parameters were measured after resting to achieve baseline haemodynamics, after 20 min moderate hypoxemia (SaO2 85 to 90%), and after a further 20 min of severe hypoxemia (SaO2 75 to 80%). Hypoxemia was induced by breathing a variable N2/O2 mixture.

MEASUREMENTS

Pulsed-wave Doppler analysis of ascending aortic blood flow was combined with phonocardiography to measure indices of systolic left ventricular function at baseline and at the end of each period of hypoxemia.

RESULTS

There was a significant, dose-related increase in cardiac output in response to hypoxemia, from 5.5 +/- 0.26 L/min at baseline to 6.1 +/- 0.08 L/min during moderate hypoxemia and to 7.0 +/- 0.23 L/min during severe hypoxemia. Likewise, heart rate increased significantly in dose-related fashion although stroke volume was not affected by either level of hypoxemia. Hypoxemia had no significant effects on systolic or diastolic blood pressures, but caused a significant reduction in systemic vascular resistance. Aortic peak and mean acceleration and acceleration time were not affected by moderate or severe hypoxemia. Although the systolic time intervals measured shortened significantly during severe hypoxemia, these were no longer significant when appropriate corrections were made for heart rate.

CONCLUSIONS

Although cardiac output increases during hypoxemia, this is due to increases in heart rate but not to any effect on stroke volume. Parameters of left ventricular systolic function and myocardial inotropic state were also not affected by severe hypoxemia. Systolic left ventricular function and myocardial contractility are thus well preserved in normal humans during hypoxemia.

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.

Usefulness of radionuclide ventriculography during transesophageal atrial pacing in the diagnosis of coronary artery disease

Radionuclide ventriculography before, during, and after atrial transesophageal pacing was carried out in 15 patients with suspected coronary artery disease (CAD) and without myocardial infarction. All patients underwent coronary angiography. Ten patients (group 1) had a coronary lesion > 50% on at least one of the main coronary arteries. Five patients (group 2) had normal coronary arteries. Radionuclide left ventricular ejection fraction (LVEF) before pacing was 56 +/- 3% in group 1 and 59 +/- 3% in group 2 (NS). Radionuclide ventriculography during pacing was 45 +/- 4% in group 1 (P < 0.0001 vs basal in group 1) and 45 +/- 6% in group 2 (P < 0.01 vs basal in group 2, NS vs group 1 during pacing). Immediate postpacing ejection fraction did not differ in the two groups and was identical to the prepacing value. A quantitative regional wall motion analysis was performed in 105 segments. Regional radionuclide ventriculography was calculated in each segment as follows: end-diastolic counts-end-systolic counts/end-diastolic counts. The relative decrease in regional LVEF during pacing was more important in the 39 segments related to a narrowed vessel than in the 66 segments related to normal coronary artery (32 +/- 13% vs 13 +/- 10%, P < 0.0001). A more than 20% relative decrease in at least one segment during pacing occurred in 10 patients in group 1 (sensitivity 100%) and in 2 patients in group 2 (specificity 60%). In conclusion, global radionuclide ventriculography during transesophageal atrial pacing decreases in patients with and without CAD.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative evaluation of left ventricular systolic function by Doppler echocardiographic techniques

Doppler echocardiography provides the ability to measure blood flow velocities noinvasively. These blood flow velocities can be used to obtain powerful hemodynamic information about systolic contractility of the left ventricle, which in the past could only be determined from invasive cardiac catheterization or cumbersome pulse recordings. Volumetric flow rates can be measured using the hydraulic principle of flow through a rigid tube, providing a measurement of stroke volume and cardiac output. The rate of the left ventricular pressure rise derived from a mitral regurgitation velocity curve provides a nonejection phase index of systolic contractility. Acceleration time can be obtained from an ascending aortic velocity and is an indicator of maximum myocardial force. Systolic time intervals can now be quickly and accurately obtained from the standard Doppler tracings. These quantitative measurements of the status of the left ventricular are accurate, reproducible, and should be incorporated into the routine noninvasive assessment of patients with cardiac disease.

Doppler echocardiography during transesophageal atrial pacing in the detection of coronary artery disease. Stress Doppler echocardiography in the detection of coronary artery disease

The aim of this study was to assess the applicability of the Doppler echocardiogram (EchoKG) during transesophageal atrial pacing (TAP) with respect to the detection of coronary artery disease (CAD). Aortic flow peak velocity (PV), mean acceleration (MA), stroke distance (SD), minute distance (MD) and time to PV were measured using pulsed Doppler EchoKG during sinus rhythm and at pacing rates of 120 and 140 bpm in 11 patients, taken as subjects, with CAD defined by coronary arteriography and 15 patients without CAD (the control group). Similar changes of PV, SD, MD and time to PV during TAP were observed in subjects with and without CAD. Only changes of MA were different between subjects with and without CAD:MA during TAP remained unchanged in the control group and decreased from 1055.2 +/- 49.7 cm/s2 (baseline) to 829.0 +/- 55.9 cm/s2 at pacing rate 140 bpm (p < 0.05) in subjects with CAD. On the basis of these data we suggest a new criterion for the detection of hemodynamically significant CAD: decrease of MA at a pacing rate of 140 bpm > 15% of initial value. Its specificity and sensitivity in the detection of CAD were respectively 87% and 82%. We conclude that the Doppler EchoKG during TAP is a relatively simple and reliable method for the diagnosis of CAD, and that the response of the Doppler EchoKG parameter of MA to TAP is a sensitive and specific index, useful for the detection of significant coronary artery stenosis.

Quantitative hemodynamics by Doppler echocardiography: a noninvasive alternative to cardiac catheterization

Doppler echocardiography has greatly enhanced the information provided by two-dimensional echocardiography. By providing information concerning pressure gradients, intracardiac pressures, volumetric flow, and diastolic filling of the heart, most hemodynamic information that in the past could be obtained only from cardiac catheterization can now be provided accurately and noninvasively by Doppler echocardiography. Future developments in instrument technology and understanding of the various Doppler velocity curves should further aid in the ability to obtain a complete, noninvasive hemodynamic assessment of the patient with cardiac disease.

Doppler-derived aortic maximal acceleration. A reliable index of left ventricular systolic function

We compared maximal acceleration of aortic blood flow (aortic Amax), calculated from maximal aortic velocity obtained with a conventional echo-Doppler machine with the invasive inotropic index left ventricular end-systolic pressure/left ventricular end-systolic volume (LVESP/LVESV) ratio and left ventricular ejection fraction (LVEF). Continuous wave (CW) and pulsed wave (PW) Doppler aortic blood flows were recorded from the apical view in 16 patients (age, 62.3 +/- 6.4 years) within 24 h of left-sided catheterization. The theoretical exponential relationship between LVEF and LVESP/LVESV was confirmed in our study population (r = 0.92; p < 0.0001). The relationship between aortic Amax determined either by CW or PW and LVESP/LVESV was linear (r = 0.92 and 0.93, respectively, p < 0.001), whereas the relationship between aortic Amax and angiographic LVEF was exponential (PW: r = 84; CW: r = 0.85; both p < 0.001). We conclude that (1) aortic Amax, derived from maximal velocity obtained with a conventional machine, can be used as an index of left ventricular systolic function, and (2) PW as well as CW Doppler signals can be used for this calculation.

Effect of increasing heart rate on Doppler indices of left ventricular performance in healthy men

OBJECTIVE

To investigate the effects of heart rate on the Doppler measurements of left ventricular function and to determine the normal pattern of rate dependency.

SETTING

University hospital specialising in internal medicine.

PARTICIPANTS

14 healthy male volunteers 10 of whom were studied.

INTERVENTION

Transoesophageal atrial pacing.

MAIN OUTCOME MEASURES

At paced rates of 70, 80, and 90 ppm the ratio of early to late peak transmitral flow velocity (E/A) was 1.97 (0.28), 1.49 (0.21), and 0.95 (0.11) respectively; the ratio of early to late time-velocity integrals of transmitral flow (Ei/Ai) was 3.03 (0.51), 2.11 (0.24), and 1.14 (0.30) respectively; and the atrial filling fraction (AFF) was 0.17 (0.03), 0.21, (0.04), and 0.24 (0.04) (mean (SD)).

RESULTS

Heart rate showed a linear correlation with E/A (r2 = 0.806), Ei/Ai (r2 = 0.838), and AFF (r2 = 0.343). Neither the peak aortic flow velocity or the mean aortic flow acceleration showed significant changes during pacing at rates of 70, 80, 90, and 100 ppm.

CONCLUSIONS

E/A and Ei/Ai can be expected to decrease by 0.5 and 0.9 for each increase of 10 beats/min in heart rate. Knowledge of this relation may be useful for the development of algorithms to correct for heart rate when diastolic function is assessed.

The relation between radionuclide angiography and Doppler echocardiography during contractile changes with infusions of epinephrine

To define the quantitative relations between radionuclide and Doppler measures of systole during sympathetic activation with epinephrine, 10 young normal men were studied with simultaneous radionuclide angiography and M-mode and Doppler echocardiography during graded infusions of epinephrine (10, 25 and 50 ng/kg/min for 12 minutes each). During a nine-fold increase in circulating levels of epinephrine in arterialized plasma (94 +/- 59 to 879 +/- 310 pg/ml, P less than 0.001), the heart rate increased from 58 +/- 8 to 73 +/- 7 beats/min (P less than 0.01), whereas the mean arterial pressure fell from 82 +/- 3 to 75 +/- 6 mmHg (NS) and end-systolic wall stress decreased from 97 +/- 6 to 67 +/- 10 dynes/sec (P less than 0.01). The ejection fraction as estimated using radionuclide techniques increased from 68 +/- 6 to 83 +/- 6%, the peak ejection rate measured in this way increased from -3.36 +/- 0.3 to -5.10 +/- 0.5 end-diastolic volumes/sec, the ejection fraction as estimated with M-mode echocardiography increased from 66 +/- 5 to 83 +/- 5%, the echocardiographic ventricular dimension shortening increased from -1.78 +/- 0.2 to -2.7 +/- 0.4 sec-1, the peak aortic outflow velocity as measured with Doppler techniques increased from 98 +/- 13 to 147 +/- 25 cm/sec, and the aortic outflow acceleration velocity increased from 11 +/- 3 to 27 +/- 7 m/sec2 (all P less than 0.001). There was a significant correlation between the changes in radionuclide and M-mode estimations of ejection fractions (r = 0.82), between the radionuclide peak ejection rate and M-mode peak dimension shortening (r = 0.80) and between the radionuclide peak ejection rate and the Doppler peak aortic outflow velocity (r = 0.90) (all P less than 0.01). We conclude that corresponding radionuclide and Doppler echocardiographic measurements of systolic function are altered similarly during increased sympathetic activation with epinephrine.

Effect of postural stress on left ventricular performance using the continuous-wave Doppler technique

To evaluate the effect of postural shifts on continuous-wave Doppler indices of left ventricular performance in normal man, we recorded Doppler signals suprasternally in 69 healthy volunteers, ranging in age from 20 to 86 years, in the supine position and 2 min after assumption of sitting and standing postures. All indices decreased progressively with increasing orthostasis: peak acceleration (PKA): 15.6 +/- 4.5 m/s2 to 14.0 +/- 4.0 m/s2 to 13.6 +/- 4.6 m/s2; peak velocity (PKV): 0.64 +/- 0.18 m/s to 0.58 +/- 0.17 m/s to 0.56 +/- 0.17 m/s; stroke distance (SD): 11.4 +/- 3.7 cm to 9.8 +/- 3.4 cm to 8.0 +/- 2.8 cm; SD x heart rate (VIH): 717 +/- 272 cm to 655 +/- 268 cm to 572 +/- 217 cm, from supine to sitting to standing, respectively (p less than 0.001). In contrast heart rate increased modestly from 62.4 +/- 10.0 bpm supine, to 66.9 +/- 12.4 bpm sitting, to 71.3 +/- 9.9 bpm standing (p less than .001). Similar postural changes in Doppler variables were seen in all three age groups (20 to 44 years; 45 to 64 years; and 65 to 86 years). Thus, orthostasis in normal subjects is accompanied by a reduction in all continuous-wave Doppler indices of left ventricular performance, regardless of age.

The effects of hormone replacement therapy in normal postmenopausal women: measurements of Doppler-derived parameters of aortic flow

In this study the effects of hormone replacement therapy on cardiac function in healthy postmenopausal women were evaluated by Doppler echocardiography that was performed before (T1) and 2.5 months after the initiation of hormone replacement therapy (T2) in the peak estrogenic phase. The following parameters of aortic flow were measured: peak flow velocity, acceleration time, and ejection time. Additional parameters were calculated: flow velocity integral and mean acceleration. The study group included 24 postmenopausal women aged 43 to 60 years (mean 51.6 years). The control group consisted of 19 postmenopausal women aged 46 to 60 years (mean 53.5 years) who were not receiving hormone replacement therapy and who underwent the same evaluation. There were no changes in all Doppler parameters between T1 and T2 in the control group. However, in the study group there were significant increases in peak flow velocity (108.3 +/- 16.7 cm/sec at T1 vs 123 +/- 20.7 cm/sec at T2; p = 0.002), flow velocity integral (17.7 +/- 3.9 vs 21.5 +/- 4.7 cm; p = 0.0003), mean acceleration (11.5 +/- 1.9 vs 13.1 +/- 2.6 m/sec/sec; p = 0.001), and ejection time (324 +/- 37.6 vs 348.8 +/- 40.7 msec; p = 0.002). There was no change in acceleration time (94.8 +/- 6.6 vs 95 +/- 10.9 msec). These results demonstrate that estrogens increase both stroke volume and flow acceleration. The latter probably reflects a combination of enhanced inotropism and vasodilatation. We assume that the cardioprotective effect of hormone replacement therapy in postmenopausal women may be due not only to changes in lipid profile but also to direct effects of estrogens on central and peripheral hemodynamic parameters.

Hemodynamic effects of calcium channel and beta-receptor antagonists: evaluation by Doppler echocardiography

To evaluate the ability of Doppler echocardiography to identify hemodynamic changes due to cardiac medications, 10 volunteers underwent Doppler examination at rest and immediately following vigorous treadmill exercise. Upon completion of the control test, each subject received moderate oral doses of propranolol, verapamil, pindolol, or nifedipine, and the same exercise protocol was repeated. During four control tests, values for peak acceleration and flow velocity integral were similar for each subject at rest and exercise. Following propranolol and pindolol, resting acceleration fell by 4.5 and 2 m/sec2, respectively p less than 0.05. Resting acceleration was unchanged by verapamil and increased following nifedipine by 1.7 m/sec2 (p less than 0.0001), but neither verapamil nor nifedipine altered either Doppler parameter. Flow velocity integral was increased by nifedipine at rest and by each of the beta-blockers during exercise (p less than 0.05). We conclude that (1) rest and exercise Doppler measurements are stable and reproducible, given stable cardiovascular status; (2) pindolol produced less hemodynamic depression as measured by Doppler echocardiography at rest relative to propranolol, but showed similar potency at maximal exertion; (3) nifedipine enhanced global cardiac performance at rest, but neither calcium antagonist affected Doppler measurements during exercise; and (4) Doppler echocardiography is a useful, noninvasive technique for evaluating hemodynamic effects of medication at rest and during vigorous exercise.

Applications of Doppler echocardiography in cardiac pacing

The purpose of this article is to review the use of Doppler echocardiography for assessing responses during cardiac pacing. Doppler techniques allow the physician to select the optimal mode pacemaker and pacemaker settings with regard to heart rate and atrioventricular delay, at rest and during exercise. Doppler parameters can be used to predict the relative hemodynamic advantage of dual chamber or rate adaptive pacing over fixed rate pacing. This valuable noninvasive modality may enhance the benefit of pacemaker therapy.

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.