Dobutamine Stress Echocardiography Identifies Patients with Angina and Dynamic Left Ventricular Outflow Obstruction in Physiological Exercise

Usefulness of Stress Echocardiography in Assessment of Dynamic Left Ventricular Obstructions: Case Series and Review of the Literature

Dynamic left ventricular outflow tract obstruction (DLVOTO) or midcavity obstruction in patients with structurally normal hearts is not uncommon in routine clinical practice and can cause significant symptoms mimicking coronary artery disease or heart failure. Although exercise echocardiography is the gold standard for assessing DLVOTO, dobutamine stress echocardiography (DSE) may be valuable diagnostic modality in patients who are unable to exercise or have an uninterpretable 12-lead electrocardiogram. We provide an updated overview of the relevant literature regarding prevalence, pathophysiology, clinical significance, and prognostic impact of DLVOTO and midcavity obstruction in structurally normal hearts. We also present a clinical series of 4 cases of DLVOTO and midcavity obstruction documented by DSE and discuss the value of different kinds of modern stress imaging modalities involving: (1) contrast-enhanced DSE to assess myocardial perfusion and inducible ischemia; (2) adenosine stress echocardiography to assess coronary flow reserve/microvascular dysfunction; and (3) functional imaging with deformation echocardiography to assess subclinical myocardial dysfunction in patients with structurally normal heart and without significant coronary disease. Based upon our own experiences and a critical review of the current literature, we will then present a practical guidance for management of DLVOTO and midcavity obstruction.

Left ventricular cavity obliteration: Mechanism of the intracavitary gradient and differentiation from hypertrophic obstructive cardiomyopathy

Background

Controversy surrounds the cause of the pressure gradient in patients with hypertrophic obstructive cardiomyopathy (HOCM). Left ventricular cavity obliteration (LVCO) was first described as the cause of the gradient but subsequently systolic anterior motion (SAM) of the mitral valve has been established as the cause. Nevertheless, the two gradients, though different in origin and significance, share similar characteristics. They both have a similar “dagger” profile, are obtained from the cardiac apex, are associated with a hyperdynamic left ventricle, and the gradients are worsened by Valsalva. The distinction has clinical relevance, because treating the intracavitary gradient (ICG) of LVCO as if it were a SAM‐associated gradient associated with HOCM would be inappropriate and possibly harmful.

Materials and Methods

To clarify the cause and characteristics of the ICG in patients with LVCO in patients without HOCM, we assessed the extent and duration of cavity obliteration, and for differentiation, we compared the spectral profiles with patients with HOCM and severe aortic stenosis (AS).

Results

Higher ICG is associated with a greater extent and more prolonged apposition of LV walls, and smaller left ventricular cavity size.

The spectral profile of patients with AS, HOCM, and LVCO is differentiated by the peak/mean gradient ratios of 2 or less, 2–3, and 3 or greater, respectively, in >90% of patients. Most patients with LVCO without HOCM or severe LVH have an ICG < 36 mm Hg.

Conclusion

The magnitude of ICG is quantitatively associated with the extent and duration of LVCO. Spectral profiles of severe AS, HOCM, and LVCO can be differentiated by the peak/mean gradient ratio.

Left ventricular cavity obliteration during dobutamine stress echocardiography in diabetic patients

Prevalence of dynamic left ventricular outflow tract obstruction (DLVO) during dobutamine stress-echo (DSE) seems disproportionally high among diabetic patients. We retrospectively identified 212 diabetic (D+) and 212 non diabetic (D-) subjects, who underwent DSE for suspected coronary artery disease (CAD); we evaluated DSE-induced DLVO prevalence and correlates. During DSE, 105 patients in D+ (50%) and 83 in D- group (39%, P = 0.032) developed a DLVO, with similar maximum gradient (94 ± 49 mmHg in D+ vs. 86 ± 49 mmHg in D-, P = NS). D+ and D- patients with DLVO showed reduced LV end-diastolic and end-systolic dimension. Compared with diabetic subjects without DLVO, diabetic patients with DLVO had higher left ventricular (LV) ejection fraction (EF), lower LV mass index; diastolic function was normal in a higher proportion of cases. Non diabetic patients with moderate or severe DLVO had higher LV EF compared with patients without DLVO. At multivariate analysis, in D+ patients, the only independent predictor was a smaller LV end-diastolic diameter (HR 0.779, CI 0.655-0.926, P = 0.005); in D- patients lower age (HR 0.878, CI 0.806-0.957, P = 0.003), higher LV EF (HR 1.087, CI 1.003-1.177, P = 0.042) and lower peak WMSI (HR 0.017, CI 0.001-0.325, P = 0.007) were associated to presence of DLVO. In D+ patients, during a median follow-up of 924 ± 134 days, we observed 11 new cardiac events, only 1 in patients with DLVO (P = 0.0041). DSE-provoked DLVO had a very high prevalence in patients evaluated for suspected CAD, especially among diabetic patients; echocardiographic predictors were a reduced LV dimension in D+ and a preserved systolic function, both at rest and at peak stress, in D- patients.

Standing position alone or in combination with exercise as a stress test to provoke left ventricular outflow tract gradient in hypertrophic cardiomyopathy and other conditions

Measuring left ventricular outflow tract (LVOT) gradient by echocardiography in decubitus position, which is used in routine clinical practice, does not reflect the pathophysiology of this dynamic abnormality during daily activities, which trigger the symptoms. LVOT obstruction is dynamic and greatly dependent upon the left ventricular cavity size, geometric configuration of hypertrophy, load, contractility and mitral apparatus abnormalities, including systolic anterior motion of mitral leaflet. Importantly, LVOT gradient may develop not only in hypertrophic cardiomyopathy, but also in other heart diseases. Recent studies show that LVOT gradient should be measured both in a standing position and during exercise.