Electromechanical interrelations during dobutamine stress in normal subjects and patients with coronary artery disease: comparison of changes in activation and inotropic state
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Published on: February 10, 2013
A M Duncan1, C A O'Sullivan, D G Gibson
1Department of Echocardiography, The Royal Brompton Hospital, Sydney Street, London SW3 6NP, UK.
Insights
Altered ventricular activation during dobutamine stress impacts left ventricular function differently in healthy individuals and coronary artery disease patients. Echocardiography and ECG distinguish activation effects from the inotropic response.
Area of Science:
- Cardiology
- Physiology
- Diagnostic Imaging
Background:
- Dobutamine stress testing is used to assess left ventricular function.
- Ventricular activation and inotropic state can influence cardiac performance.
- Distinguishing these effects is crucial for accurate diagnosis.
Purpose of the Study:
- To investigate the effects of altered ventricular activation during dobutamine stress on left ventricular function.
- To differentiate these effects from the inotropic response in normal subjects and CAD patients.
Main Methods:
- Prospective analysis of 12-lead ECG and echocardiography at rest and peak stress.
- Doppler echocardiography assessed left ventricular ejection and filling patterns.
- Correlated activation effects with ejection/filling times and Z ratio; measured inotropic response via peak aortic acceleration.
Main Results:
- In controls, QRS shortened, Z ratio increased, and peak aortic acceleration (PAA) rose significantly.
- In CAD patients, QRS lengthened, Z ratio decreased, but PAA still increased.
- Changes in ejection and filling times reflected ventricular activation, independent of inotropic state.
Conclusions:
- Relative ejection and filling times indicate ventricular activation during dobutamine stress, irrespective of inotropic changes.
- Peak aortic acceleration reflects dobutamine's positive inotropic effect, independent of activation alterations.
Objective:
To identify the effects of altered ventricular activation during dobutamine stress on left ventricular function in normal subjects and in patients with coronary artery disease, and to distinguish these from an inotropic response.
Design:
Prospective analysis of 12 lead ECG and echocardiogram at rest and at peak stress.
Setting:
Tertiary referral centre for cardiac disease equipped with non-invasive facilities for pharmacological stress testing.
Methods:
22 patients with coronary artery disease were compared with 17 age matched controls. Left ventricular ejection and filling patterns were assessed using Doppler echocardiography. Activation effects were correlated with relative left ventricular ejection and filling times, and the Z ratio ([left ventricular ejection + filling times]/RR interval). Inotropic response was measured from peak aortic acceleration.
Results:
In controls, QRS shortened (by 4 ms, p < 0.001), and total ejection and filling periods lengthened (by 2 s/min, p < 0.01 and 5 s/min, p < 0.001, respectively). The Z ratio thus increased and correlated with QRS shortening (r(2) = 0.69). Peak aortic acceleration (PAA) increased by 135%, p < 0.001. In patients, QRS lengthened at peak stress (by 9 ms, p < 0.001). Total ejection and filling times did not change, but Z ratio fell, correlating with QRS prolongation (r(2) = 0.65). Nevertheless, PAA increased by 63%, p < 0.001.
Conclusions:
Relative ejection and filling times reflect ventricular activation at rest and during stress independent of changes in inotropic state. By contrast, peak aortic acceleration reflects the positive inotropic effect of dobutamine on the myocardium, regardless of changes in activation.
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