Pronounced reduction of aortic flow velocity and acceleration during heavy isometric exercise in coronary artery disease

Noninvasive pulmonary arterial pressure estimation using a logistic-based systolic model

RATIONALE

A hemodynamic relationship of pulmonary artery pressure (PAP) to pulmonary acceleration time (PAcT) has not yet been explicitly presented.

OBJECTIVE

We employed a logistic-based systolic model with a subtle modification for pulmonary circulation and provided a logical ground for the relationship between systolic PAP and PAcT using transthoracic echocardiography. Additionally, the logistic-based PAP estimation equation was deduced from the model to relate systolic PAP and PAcT.

METHODS AND RESULTS

This equation was statistically tested in comparison to existing PAP estimation equations. Results showed that the logistic-based PAP estimation equation was at least as accurate as previous equations with respect to previously published mean PAP versus PAcT values. After the subtle pulmonary modification of the model, the pulmonary blood flow velocity and pressure not only well reflected the underlying pulmonary circulation physiology, but could also be presented in harmony with systemic circulation physiology.

CONCLUSIONS

A future clinical study with actual systolic PAP versus PAcT measurements is needed to test the application of the logistic-based PAP estimation equation.

Exercise-induced aortic flow parameters in early postmenopausal women and middle-aged men

OBJECTIVE

Exercise Doppler echocardiography has been recognised as an accurate method for the assessment of left ventricular function in patients with coronary artery disease. Gender differences in aortic flow parameters during exercise have not been well established. The aims of this study were to compare basal ejection Doppler indexes in healthy early postmenopausal women with those of men, and to assess the effects of both isometric and dynamic exercises on these parameters.

DESIGN

Intergroup comparison between early postmenopausal women and middle-aged men.

SUBJECTS

Fifteen healthy women with a mean age of 55 (SD 5) years and 15 healthy men aged 52 (SD 4) were evaluated.

SETTING

Women were recruited from a menopause clinic and men from a primary cardiovascular prevention program at a cardiac rehabilitation institute.

INTERVENTIONS

Isometric exercise was performed with a 2-hand bar dynamometer, and dynamic exercise with a supine ergometer. Echo Doppler examination was performed at rest and at peak isometric and dynamic exercise with a pulsed Doppler transducer.

RESULTS

Both types of exercise resulted in higher values of hemodynamic parameters in the women, with most figures reaching statistical significance. Most aortic flow parameters during rest and exercise were also significantly higher in the women.

CONCLUSIONS

The unexpected higher values in hemodynamic and aortic flow parameters in early postmenopausal women as compared with middle aged men may shed light on a peculiar aspect of gender differences in cardiovascular function, perhaps specific to this age group and related to menopausal transition.

Comparison of left ventricular function using isometric exercise Doppler echocardiography in competitive runners and weightlifters versus sedentary individuals

It is unclear whether cardiovascular responses to heavy isometric exercise are changed by intensive training. We evaluated the effects of this type of exercise on left ventricular (LV) function in athletes engaged in static and dynamic sport, compared with sedentary persons, and looked for peculiarities in static athletes' responses that might reflect adaptive mechanisms to their specific activity. The study population comprised 45 men (age 24 +/- 5 years): 29 dynamic and 16 static athletes (runners and weightlifters, respectively). The control group consisted of 20 age and gender-matched healthy sedentary persons. All performed 50% of maximal voluntary contraction on a whole-body isometric exercise device for 2 minutes. Echocardiographic calculations were determined at rest and exercise. Upon exercise, stroke volume, cardiac output, end-diastolic volume, and ejection fraction increased significantly in athletes, while end-systolic volume and systemic vascular resistance decreased. In sedentary persons, stroke volume and resistance remained unchanged, cardiac output and LV volumes increased, and ejection fraction decreased from 67 +/- 5% to 60 +/- 5% (p <0.01 compared with rest; p <0.0001 compared with athletes). Whereas peak flow velocity decreased from 103 +/- 10 to 81 +/- 6 cm/s in sedentary persons, it increased from 112 +/- 9 to 126 +/- 8 cm/s in the static group and from 120 +/-3 to 126 +/- 9 cm/s in the dynamic athletes (p <0.0001 compared with the sedentary group). Mean acceleration decreased in the sedentary group, remained unchanged among the dynamic athletes, and increased among the static athletes. We conclude that cardiovascular responses to heavy isometric exercise are modified by intensive training. Athletes, taken as a group, react differently and adapt better than sedentary individuals. Moreover, among them, those involved in static sport show an improved cardiovascular adaptation to this type of exercise.

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.

Angiotensin-converting enzyme inhibition, autonomic activity, and hemodynamics in patients with heart failure who perform isometric exercise

Effects of angiotensin-converting enzyme inhibition (ACEI) on autonomic responses and hemodynamics in patients with congestive heart failure (CHF) subjected to isometric exercise have not been studied. We tested whether acute ACEI might influence the effects of isometric exercise in patients with CHF. In the first part of the study we showed that isometric exercise increased blood pressure in the control group and in the CHF group, whereas cardiac output increased only in the control group. Stroke volume remained unchanged in the control group, whereas it decreased significantly in CHF group. We next analyzed the effect of acute ACEI (5 mg ramipril) on the decrease in cardiac output during isometric stress in patients with CHF. During isometric exercise mean blood pressure and heart rate increased similarly in both groups. However, cardiac output decreased during placebo by -0.48 +/- 0.12 L/min (p < 0.01) but not during ACEI. Spectral analysis of blood pressure showed an increase (p < 0.01) in the high-frequency parasympathetic component from 7.3% +/- 3.6% to 18.1% +/- 9.5% after ACEI. norepinephrine plasma levels increased after isometric stress in the placebo group, whereas other hormones did not change. ACEI prevented the norepinephrine increase after isometric stress. Thus the decrease in cardiac output during isometric exercise in patients with CHF was prevented by acute ACEI. The effect of ACE inhibition may be related to reduced sympathetic activity.

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.

Long-term effects of hormone replacement therapy on Doppler-derived parameters of aortic flow in postmenopausal women

Eighteen postmenopausal women were examined by Doppler echocardiography before initiation of HRT (T1), then after ten weeks (T2) and one year (T3). This study group was compared with another in which HRT was not used. Flow velocity integral, which correlates with SV, and MA, an indicator of cardiac contractility, were calculated. In the study group, PFV was 107 +/- 18 cm/s at T1 and increased significantly at T2 and T3. Ejection time, which was prolonged at T2 compared to T1, returned to its basal value at T3. Flow velocity integral increased at T2, but this change was only partially sustained at T3. Mean acceleration maintained its increase throughout T2 to T3. None of the Doppler parameters showed a significant change in the controls from T1 to T3. Our results suggest that the peripheral hemodynamic effects of HRT, such as vasodilatation, are transient, whereas the central effects (increased inotropism) are long-lasting.

Usefulness of heavy isometric exercise echocardiography for assessing left ventricular wall motion patterns late (> or = 6 months) after acute myocardial infarction

The aim of this prospective study was to determine the effects of heavy isometric exercise on left ventricular (LV) wall motion patterns in patients who have had myocardial infarction, and to compare heavy isometric exercise with dynamic exercise for competence in eliciting LV wall motion abnormalities at equivalent rate-pressure products. Echocardiography was performed in 42 patients during supine bicycle ergometry and during heavy dynamometer stretching at 50% of maximal voluntary contraction. Systemic vascular resistance increased from 1,484 to 1,649 dynes s cm-5 (p < 0.05) during isometric exercise, and decreased significantly during dynamic exercise. Wall motion abnormalities or new asynergy were induced by isometric exercise in 120 segments, 107 of which (89%) showed significant stenosis of the perfusing coronary artery. Hypokinesia was the dominant pattern in the range of 76 to 90% narrowing; akinesia was dominant at 91 to 100% narrowing. Wall motion abnormalities were also documented in 13 segments (11%) assumed to be supplied by vessels with nonsignificant stenosis. Dyskinesia, seen in 7% of the segments, was equally distributed between both groups with significant stenosis. Sensitivity and positive predictive value in identifying specific coronary vessel disease was similar for both isometric and dynamic exercise. In conclusion, heavy isometric exercise in patients who have had myocardial infarction induces wall motion abnormalities of a severity proportional to the degree of coronary narrowing. This exercise method is similar to dynamic exercise for ability in identifying obstructions in a specific vessel. Furthermore, when compared at near-equal rate-pressure products, heavy isometric exercise is far superior in sensitivity to dynamic exercise.

Doppler-derived aortic flow measurements during and after heavy isometric exercise in healthy men versus men with myocardial infarction

Doppler echocardiography is a useful noninvasive determination of left ventricular function during dynamic exercise. Scarce data are available for the use of this technique during heavy isometric exercise. Therefore, Doppler-derived aortic flow indexes were assessed during and after 50% maximal upper-body isometric exercise in 25 healthy men (aged 47 +/- 6 years) and compared with those of 22 men (aged 48 +/- 9 years) who had suffered myocardial infarction. The heart rate increased (p = 0.01) in each of the groups from a mean of 68 +/- 12 at rest to 84 +/- 11 during isometric exercise. At rest, systolic blood pressure was higher (p = 0.05) in the patients with coronary artery disease. During exercise, the patients with cardiac disease, compared with the healthy volunteers, demonstrated a lesser reduction in flow velocity integral, stroke volume, and cardiac indexes (p = 0.001). Immediately on recovery, the patients with cardiac disease, compared with the healthy group, showed significantly greater (p = 0.001) increase in stroke volume and cardiac indexes. At 3 minute's recovery, the stroke volume index continued to increase in the patients with cardiac disease, while the healthy group showed a decrease to below its resting value. Although 50% of maximal upper-body isometric exercise caused similar heart rate and systolic blood pressure responses in healthy patients and patients with cardiac disease, there were significant group differences in Doppler-derived left ventricular systolic function indexes, which were greatest on immediate and 3 minute's recovery. The results suggest that this novel isometric test may be useful in clinical testing.