Hypotensive response during dobutamine stress echocardiography in coronary patients: a common event of well-functioning left ventricle

The susceptibility of cardiac arrhythmias after spinal cord crush injury in rats

High-level spinal cord injury (SCI) often interrupts supraspinal regulation of sympathetic input to the heart. Although it is known that dysregulated autonomic control increases the risk for cardiac disorders, the mechanisms mediating SCI-induced arrhythmias are poorly understood. Here, we employed a rat model of complete spinal cord crush injury at the 2nd/3rd thoracic (T2/3) level to investigate cardiac rhythm disorders resulting from SCI. Rats with T9 injury and naïve animals served as two controls. Four weeks after SCI, rats were implanted with a radio-telemetric device for electrocardiogram and blood pressure monitoring. During 24-h recordings, heart rate variability in rats with T2/3 but not T9 injury exhibited a significant reduction in the time domain, and a decrease in power at low frequency but increased power at high frequency in the frequency domain which indicates reduced sympathetic and increased parasympathetic outflow to the heart. Pharmacological blockade of the sympathetic or parasympathetic branches confirmed the imbalance of cardiac autonomic control. Activation of sympatho-vagal input during the induction of autonomic dysreflexia by colorectal distention triggered various severe arrhythmic events in T2/3 injured rats. Meanwhile, intravenous infusion of the β1-adrenergic receptor agonist, dobutamine, caused greater incidence of arrhythmias in rats with T2/3 injury than naïve and T9 injured controls. Together, the results indicate that high-level SCI increases the susceptibility to developing cardiac arrhythmias likely owing to compromised autonomic homeostasis. The T2/3 crush model is appropriate for studying abnormal cardiac electrophysiology resulting from SCI.

Low-Dose Dobutamine Stress Echocardiography for the Early Detection of Pulmonary Arterial Hypertension in Selected Patients with Systemic Sclerosis Whose Resting Echocardiography Is Non-Diagnostic for Pulmonary Hypertension

BACKGROUND

Dobutamine stress echocardiography (DSE) has limited application in systemic sclerosis (SSc). We examined DSE usefulness in revealing pulmonary arterial hypertension (PAH) in selected SSc patients whose resting echocardiography for pulmonary hypertension (PH) was non-diagnostic.

METHODS

Forty SSc patients underwent right heart catheterization (RHC) and, simultaneously, low-dose DSE (incremental doses up to 20 μg/kg/min). Inclusion criteria were: preserved left and right ventricular (RV) function (tricuspid annulus plane systolic excursion [TAPSE] ≥ 16 mm and tissue Doppler imaging-derived systolic velocity of tricuspid annulus [RVS'] > 10 cm/s), normal pulmonary function tests, and baseline maximal tricuspid regurgitation (TR) velocity of 2.7-3.2 m/s.

RESULTS

Of 36 patients who completed DSE, resting RHC diagnosed PAH in 12 patients (33.3%). At 20 μg/kg/min, patients with PAH had higher TR velocity, higher pulmonary arterial pressure measured by RHC, and lower RV inotropic response compared with patients without PAH. A cut-off value of maximal TR velocity >3.1 m/s had a sensitivity of 80%, a specificity of 84.2%, and an accuracy of 82.4% for the detection of PAH.

CONCLUSIONS

Low-dose DSE has a satisfactory diagnostic accuracy for the early detection of PAH in highly selected SSc patients whose baseline echocardiographic measurements for PH lie in the gray zone.

Frequency, Predictors, and Implications of Abnormal Blood Pressure Responses During Dobutamine Stress Echocardiography

BACKGROUND

It is not known whether abnormal blood pressure (BP) responses during dobutamine stress echocardiography (DSE) are associated with abnormal test results, nor if such results indicate obstructive coronary artery disease (CAD). We sought to define the frequency of abnormal BP responses during DSE and their impact on accuracy of test results.

METHODS AND RESULTS

We studied 21 949 patients who underwent DSE at Mayo Clinic, Rochester, MN, grouped by peak systolic BP achieved during the test. We also analyzed a subgroup who underwent coronary angiography within 30 days after positive DSE. The positive predictive value of DSE was calculated for each BP group. Patients with hypertensive response (n=1905; 9%) were more likely to have positive DSE than those with normal (n=19 770; 90%) or hypotensive (n=274; 1%) BP responses (32% versus 21% versus 23%, respectively; P<0.0001). Angiography, performed in 1126 patients, showed obstructive CAD (≥50% stenosis) in 814 patients and severe CAD (≥70% stenosis) in 708 patients. Positive predictive value of DSE was similar for patients who had hypertensive and normal BP responses (69% versus 73%; P=0.3), considering 50% stenosis cut point. The proportion of severe CAD (≥70% stenosis) was lower in patients who had hypertensive response compared with those who had normal BP response (54% versus 65%; P=0.005).

CONCLUSIONS

Patients with hypertensive response during DSE are more likely to have stress-induced myocardial ischemia compared with those with normal or hypotensive BP responses but are not more likely to have false-positive DSE results. They are, however, less likely to have higher grade or multivessel CAD.

Significance of hypotensive response during dobutamine stress echocardiography

BACKGROUND

In patients undergoing exercise testing a hypotensive response is associated with a poor prognosis. There is limited information regarding the prognostic significance of hypotension during dobutamine stress test. This study investigates the association between a severe hypotensive response during DSE and long-term prognosis.

METHODS

Patients (3381) underwent dobutamine stress echocardiography (DSE). Blood pressure was measured automatically at rest and at the end of every dose-step. Wall motion was scored using a 16-segement, 5-point score. Ischemia was defined by the presence of new wall motion abnormalities. Hypotensive response during DSE was defined as mild (MHR) when systolic blood pressure (SBP) dropped <20 mmHg between rest and peak stress, and severe (SHR) when SBP dropped <20 mmHg. During follow-up all cause mortality and MACE (cardiac death or non-fatal myocardial infarction) were noted.

RESULTS

MHR and SHR occurred in 936 (28%) and 521 (15%) patients, respectively. Independent predictors of SHR were older age, new or worsening wall motion abnormalities and history of hypertension. During follow-up of 4.5 (+/-3.3) years, 920 patients died, of which 555 due to cardiac causes, and 713 patients experienced a MACE. After adjustment for baseline characteristics and DSE results SHR during DSE was independently associated with increased long-term cardiac death (HR: 1.3, 95% CI: 1.03-1.6) and MACE (HR: 1.34, 95% CI: 1.1-1.6), while MHR was not associated with a worse outcome.

CONCLUSIONS

Severe hypotensive response during DSE independently predicts cardiac death and MACE in patients with known or suspected coronary artery disease.

[Cardiac asystole during acute anterior myocardial infarction: a consequence of endocardiac reflexes]

The authors report a case of paroxysmal, complete atrioventricular block during an anterior acute myocardial infarction, leading to asystolia. The different possible physiopathological mechanisms are discussed, suggesting a paroxysmal nodal conduction defect, secondary to transient parasympathetic stimulation, triggered by a Bezold-Jarish type of cardiac reflex. This reflex is frequently involved in various pathologic situations or diagnostic procedures, usual in cardiology. Although it is frequently observed in inferior myocardial infarction, it can occur during an anterior acute myocardial infarction.

Regional Response of Myocardial Acceleration During Isovolumic Contraction During Dobutamine Stress Echocardiography: A Color Tissue Doppler Study and Comparison with Angiocardiographic Findings

BACKGROUND

Color tissue Doppler imaging permits noninvasive quantitation of regional wall motion. In experimental studies, a new marker, the slope of the isovolumic contraction wave, isovolumic acceleration (IVA) was more insensitive to ventricular loading conditions than myocardial velocities. This study compared the regional response IVA to dobutamine stress echocardiography to angiographic findings.

METHODS

The Myocardial Doppler in Stress Echocardiography (MYDISE) study prospectively recruited 149 consecutive patients with chest pain for dobutamine stress tissue Doppler echocardiography prior to coronary angiography. This color tissue Doppler database was analyzed for IVA in 1,192 basal and mid segments at rest and again at peak stress. Angiographic findings were compared to IVA and peak systolic velocities (PSV) in corresponding cardiac segments. The diagnostic accuracy of IVA to predict coronary artery stenosis was determined using cut-off values for three representative segments and with the MYDISE diagnostic model including eight segments.

RESULTS

Regional IVA increased in a dose-dependent manner during dobutamine infusion. The response was blunted in the supply territory of stenosed coronary artery branches. IVA performed slightly better than PSV as single marker for coronary artery stenosis. A diagnostic model incorporating IVA and PSV was 85-95% accurate (area under receiver operating characterstic curves).

CONCLUSIONS

Regional changes of isovolumic acceleration during dobutamine stress echocardiography reflect regional wall motion and can be used to predict coronary artery stenosis with similar accuracy as a model based on systolic myocardial velocities. As a single marker, IVA performed better than myocardial velocities.

Dobutamine-induced bradycardia in a dog

An otherwise healthy 8-year-old neutered male, mixed breed dog was anesthetized for surgical removal of multiple uroliths. Pre-anesthetic medication was midazolam, glycopyrrolate, and morphine. Anesthesia was induced with propofol and maintained with isoflurane in oxygen. One hour after induction, the patient moved and propofol was administered. Subsequently, the patient developed hypotension. Dobutamine administered at this time produced a rapid and profound decrease in heart rate that was treated successfully with atropine. The bradycardia in this case may be the result of the Bezold-Jarisch reflex, an intracardiac parasympathetic nervous reflex. Discontinuation of dobutamine and/or administration of a parasympatholytic drug should be performed if bradycardia occurs during dobutamine infusion.