The clinical impact of dynamic intraventricular obstruction during dobutamine stress echocardiography

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.

Comparison of Valsalva Maneuver, Amyl Nitrite, and Exercise Echocardiography to Demonstrate Latent Left Ventricular Outflow Obstruction in Hypertrophic Cardiomyopathy

Guidelines recommend exercise stress echocardiogram (ESE) for patients with hypertrophic cardiomyopathy (HC) if a 50 mm Hg gradient is not present at rest or provoked with Valsalva or amyl nitrite, to direct medical and surgical management. However, no study has directly compared all 3 methods. We sought to evaluate efficacy and degree of provocation of left ventricular outflow gradients by ESE, and compare with Valsalva and amyl nitrite. In patients with HC between 2002 and 2015, resting echocardiograms and ESEs within 1 year were retrospectively reviewed. Gradients elicited by each provocation method were compared. Rest and ESE were available in 97 patients (mean age 54 ± 18 years, 57% male); 78 underwent Valsalva maneuver and 41 amyl nitrite provocation. Median gradients (interquartile range) were 10 mm Hg (7,19) at rest, 16 mm Hg (9,34) with Valsalva, 23 mm Hg (13,49) with amyl nitrite, and 26 mm Hg (13,58) with ESE. ESE and amyl nitrite were able to provoke obstruction (≥30 mm Hg) and severe obstruction (≥50 mm Hg) more frequently than Valsalva. In patients with resting gradient <30 mm Hg (n = 83), provocation maneuvers demonstrated dynamic obstruction in 51%; in those with Valsalva gradient <30 mm Hg (n = 57), ESE or amyl nitrite provoked a gradient in 44%; and in those with amyl nitrite gradient <30 mm Hg (n = 20), ESE provoked a gradient in 29%. No demographic or baseline echocardiographic parameter predicted provocable obstruction. In conclusion, ESE is clinically useful; however, different provocation maneuvers may be effective in different patients with HC, and all maneuvers may be required to provoke dynamic obstruction in symptomatic patients.

Comparing exercise training modalities in heart failure: A systematic review and meta-analysis

Exercise training (ET) is suggested to improve exercise capacity, prognosis, quality of life (QOL) and functional modifications of the heart in patients with heart failure (HF). However, it is not clear which modality is best. In order to assess the effectiveness of different ET modalities on prognostic cardiopulmonary exercise test (CPET) parameters, QOL and left ventricular remodeling, a systematic review and meta-analysis was performed. Randomized clinical trials (RCTs) were selected in three databases. The primary outcome data were peak oxygen uptake, ventilation over carbon dioxide slope, oxygen uptake efficiency slope, exercise oscillatory ventilation, rest and peak pulmonary end-tidal CO2. Secondary variables were QOL, left ventricular ejection fraction (LVEF) and left ventricular end-diastolic diameter (LVEDD). Twenty RCTs (n=811) met the a priori stated inclusion criteria. Studies were categorized into four different groups: "interval training (IT1) versus combined interval and strength training (IT1S)" (n=156), "continuous training (CT1) versus combined continuous and strength training (CT1S)" (n=130), "interval training (IT2) versus continuous training (CT2)" (n=501) and "continuous training (CT3) versus strength training (S3)" (n=24). No significant random effects of exercise modality were revealed assessing the CPET parameters. There was a significant improvement in QOL applying CT1S (P<0.001). Comparing IT2 with CT2, LVEDD and LVEF were significantly improved favoring IT2 (P<0.001). There is some evidence to support that interval training is more effective to improve LVEF and LVEDD. The fact that patients with HF are actively involved in any kind of ET program seems sufficient to improve the prognosis, QOL and anatomic function.

Basic echocardiographic features of patients with latent left ventricular outflow tract obstruction without left ventricular hypertrophy

Left ventricular outflow tract obstruction (LVOTO) is commonly observed in patients with hypertrophic cardiomyopathy (HCM) or left ventricular hypertrophy (LVH). While some patients develop LVOTO at rest, it can also be provoked by physical exertion, and hence termed latent LVOTO (L-LVOTO). Recent reports demonstrated that L-LVOTO develops not only in LVH patients, but also in patients without LVH (non-LVH). However, the prevalence and clinical prognosis of non-LVH patients with L-LVOTO are not yet elucidated. In this study, we retrospectively investigated the echocardiographic features of patients with malignancy who underwent dobutamine stress echocardiography (DSE) to evaluate preoperative cardiac risk. One hundred ninety-nine patients were found not to have LVH or coronary artery disease. Among them, 106 patients exhibited L-LVOTO after DSE. We next compared the baseline echocardiographic features of L-LVOTO (+) patients with those of L-LVOTO (-) patients, and identified the left ventricular outflow tract (LVOT) ratio (systolic LVOT diameter/diastolic LVOT diameter) as a significant predictor of L-LVOTO. An LVOT ratio ≤ 0.83 was the best cutoff value to detect the presence of L-LVOTO, with a sensitivity of 81.1% and specificity of 80.6%. Overall, L-LVOTO was found to develop in almost half of non-LVH patients with malignancy. In addition, the baseline LVOT ratio was strongly related to the presence of L-LVOTO in non-LVH patients. Therefore, patients with dynamic LVOT narrowing may benefit from DSE to detect the presence of L-LVOTO.

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.

Left ventricular outflow tract and mid-cavity obstruction may cause false-positive dobutamine stress echocardiograms

Left ventricular (LV) outflow tract obstruction (LVOTO) occurs in up to 20% of patients undergoing dobutamine stress echocardiography (DSE). Mid-cavity LV obstruction occurs less commonly during DSE. LV regional wall motion abnormalities during DSE may occur despite normal coronaries due to hypertensive blood pressure response and takotsubo stress cardiomyopathy. We describe herein two cases of LVOTO and one case of mid-cavity LV obstruction during DSE associated with transient apical hypokinesis.

Effort angina, normal coronary angiogram, and dynamic left ventricular obstruction

The development of dynamic left ventricular outflow tract (LVOT) obstruction (DLVOTO) during effort in patients without hypertrophic cardiomyopathy has been described only a few times and its clinical significance has not been established. This study was undertaken to determine DLVOTO during exercise in patients with angina and normal coronary arteries, and to analyze the potential mechanism involved. The study included 23 patients (60.7 +/- 7.2 years), with effort angina and normal coronary arteries who underwent exercise echocardiography. DLVOTO during exercise appeared in 7 patients (30.4%), with gradients ranging from 31.1 to 67.2 mm Hg (mean 41.3 +/- 12.6). These patients showed more symptoms (effort angina) during testing than the remaining patients (100% vs 47.3%; P = .014). LVOT size was the only predictive factor of DLVOTO (9.1 +/- 0.5 vs 10.3 +/- 1.2 mm/m(2); P = .017). In patients with angina and no epicardical coronary artery disease DLVOTO is associated with a lower LVOT size.

Beta-blocker therapy for dynamic left ventricular outflow tract obstruction induced by exercise

BACKGROUND

In patients who present with angina, dynamic left ventricular outflow tract obstruction may be responsible of symptoms. The aim of our study was to evaluate the effect of negative inotropic therapy on ventricular physiology and symptoms of patients with dynamic left ventricular outflow tract obstruction induced by exercise in the absence of hypertrophic cardiomyopathy.

METHODS

Seventy eight patients with symptoms of angina, normal exercise SPECT test and normal resting left ventricular systolic function were prospectively analysed with exercise echocardiography. Fifteen of them developed high outflow tract velocities (greater than 2.57 m/s) on effort. After treatment with bisoprolol (mean dose 6.9+/-3.5 mg) in these patients, symptoms and dynamic left ventricular outflow tract obstruction during exercise were re-evaluated.

RESULTS

After negative inotropic therapy, there was a significant reduction of 86.6% in the development of intracavitary gradient (15 to 2 patients). In all patients the left ventricular outflow tract velocities decreased (2.91+/-0.4 m/s to 1.92+/-0.46 m/s, p=0.001). However, the oxygen consumption during exercise was higher (7.3+/-1.7 METs to 8.5+/-1.8 METs, p=0.005), and symptoms improved significantly following therapy, with a reduction in mean NYHA class from 1.9+/-0.5 to 1.0+/-0.0 (p=0.001).

CONCLUSIONS

Negative inotropic therapy may represent a beneficial therapeutic approach in selected patients with dynamic left ventricular outflow tract obstruction induced by exercise and identified during exercise echocardiography.

Left ventricular outflow tract obstruction provoked during dobutamine stress echocardiography predicts future chest pain, syncope, and near syncope

BACKGROUND

Although dobutamine stress echocardiography (DSE) is associated with dynamic left ventricular (LV) obstruction, it is unknown whether such obstructive event, in general, and the specific site of obstruction, in particular, have unique clinical prognostic significance. We sought to determine whether dynamic LV outflow tract (LVOT) versus LV midcavitary obstruction provoked during DSE would predict future chest pain, syncope, and/or near syncope.

METHODS

Two hundred thirty-seven patients (145 men and 92 women, mean age 58 +/- 13 [+/-SD] years) without DSE-provoked ischemia underwent continuous wave Doppler interrogation to detect any inducible dynamic flow obstruction. Patients were prospectively followed for a mean duration of 31 +/- 13 months.

RESULTS

One hundred fifty-four of 237 patients had no provoked LV obstruction (group 1). Fifty-four (22.8%) had provoked LV midcavitary (group 2) obstruction, and 29 (12.2%) had outflow tract (group 3) obstruction. During follow-up, chest pain occurred more frequently in groups 2 (46%, P < .05) and 3 (52%, P = .05) as compared with group 1 (31%). A higher incidence of syncope and/or near syncope was noted in group 3 (21% vs 9% in group 1). LVOT obstruction but not midcavitary obstruction was a significant predictor of future chest pain (relative risk 2.63, P = .0021) and syncope and/or near syncope (relative risk 3.11, P = .036). Kaplan-Meier analysis showed a significantly less event-free survival (P = .025) for the combined end point of chest pain, syncope, and/or near syncope in patients with LVOT obstruction.

CONCLUSIONS

This is the first prospective study to identify the differential prognostic implications of the site of dynamic obstruction noted during DSE. Our results demonstrate that DSE-provoked LVOT obstruction is an independent positive predictor of future episodes of chest pain and syncope and/or near syncope. These findings warrant larger studies addressing treatment options to ameliorate symptoms in this subgroup of patients.

Significance of systolic anterior motion of the mitral valve during dobutamine stress echocardiography

Left ventricular outflow tract obstruction related to systolic anterior motion of the mitral valve (SAM) induced during dobutamine stress echocardiography (DSE) is not unusual but its significance is not established. A total of 100 consecutive patients (mean age 62 +/- 12 years; 67% male) without previous transmural myocardial infarction, valvular disease, or hypertrophic cardiomyopathy, undergoing DSE to assess the presence of myocardial ischemia, were prospectively evaluated. A SAM with DSE was searched and correlated with clinical and baseline echocardiographic findings. Patients who demonstrated SAM with DSE were selected for exercise echocardiographic Doppler study with bicycle, within 6 months of the DSE. The development of an intraventricular gradient with DSE or exercise was defined as a new gradient of > or =36 mm Hg. In all, 23 patients developed SAM during DSE with a mean gradient of 79 +/- 33 mm Hg (range: 39-144 mm Hg) and mitral regurgitation related to SAM. Compared with patients without SAM, patients who developed SAM with DSE were characterized at rest by a smaller mitroaortic angle and septoaortic angle, a higher posterior mitral leaflet length, and a smaller left ventricular cavity. Neither ischemic nor hypotensive response during DSE were correlated to SAM. In the group of patients with SAM, of the 9 patients who were referred for unexplained chest pain or dyspnea, 5 reproduced symptoms with DSE, compared with 2 of 17 patients in the group without SAM (P = .005). Despite these findings, only 3 of the 16 patients who underwent exercise echocardiography Doppler study developed SAM (two with symptoms), with a wide range of achieved heart rate, compared with DSE. Although patients with SAM with DSE exhibit predisposing echocardiographic findings, the clinical impact of this phenomenon is real in only a minority of patients, particularly those who experienced unexplained dyspnea or chest pain.

Dobutamine stress echocardiography in women with systemic lupus erythematosus: increased occurrence of left ventricular outflow gradient

Dobutamine stress echocardiography (DSE) is an accurate noninvasive test used for the diagnosis and evaluation of patients with known or suspected coronary artery disease (CAD). The aim of this study was to determine the rate of positive findings in DSE, to define the echocardiographic and clinical characteristics of women with systemic lupus erythematosus (SLE) and to evaluate the safety of DSE in SLE patients. Thirty consecutive SLE patients were enrolled in the study and underwent DSE study. The mean age of patients was 44 years (range 20-76). Mean duration of SLE was 8.1 years and mean SLEDAI was 5.5. None of the DSE tests performed were positive for myocardial ischaemia. A left ventricular outflow gradient (LVOG) was found in 15/28 (54%) patients who completed the test, a result higher than the reported 20% prevalence of this finding in the literature. There were no significant differences in baseline characteristics between patients who developed a gradient and patients in whom a gradient was not found. There were no significant adverse effects during the study. In the general population, LVOG has been reported to be associated with an increased rate of chest discomfort and with a significantly lower prevalence of CAD. Whether this is true for SLE patients requires further study.

Dobutamine-inducible left ventricular obstruction: head-up tilt and autonomic balance

BACKGROUND

Dobutamine-inducible left ventricular obstruction lacks a sound clinical meaning. This phenomenon may be related to an abnormal response of the heart to the sympathetic stimulation, and head-up tilt would elicit intraventricular obstruction in patients known to develop it during dobutamine administration, through the synergistic effects of reduced preload, hypercontractility, and reflex increase in the cardiac sympathetic tone.

METHODS

Twenty-one patients with normal coronaries and available dobutamine stress-echocardiography underwent 60 degrees -head-up tilt on echocardiographic and electrocardiographic monitoring in drug-free and nitroglycerin infusion (0.3 mcg/kg/min) protocols. Twelve patients had (group 1: 7 males, aged 61+/-7 years), and nine had not (group 2: 3 males, aged 60+/-9 years) developed left ventricular obstruction during dobutamine stress-echocardiography. Doppler echocardiographic measurements of left ventricular diameters, function and outflow tract flow velocity were performed; power heart rate variability was analysed on short electrocardiographic recordings (low/high frequency ratio); plasma catecholamines were determined at baseline and during the tilt manoeuvres.

RESULTS

Intraventricular obstruction did not develop in group 1. There were baseline differences in ventricular dimensions and mitral early-to-late velocity ratio between group 1 and 2, but hemodynamic behaviour during either tilt manoeuvre was similar. Low/high frequency ratio, that was similar at baseline and similarly increased on head-up tilt, increased significantly less on nitroglycerin-tilt in group 1. No difference in plasma catecholamines was found.

CONCLUSIONS

Reflex cardiovascular adaptive responses as those elicited by passive tilt are not involved in dynamic intraventricular obstruction in dobutamine-inducible obstruction patients, data indicating that left ventricular geometry and hypercontractility are not sufficient pathophysiological determinants.

Beta-blocker therapy for dynamic left-ventricular outflow tract obstruction

BACKGROUND

In a small but significant group of elderly patients who present with breathlessness, dynamic left-ventricular outflow tract obstruction (DLVOTO) may be responsible for symptom generation. The aim of our study was to investigate the effect of beta-blockade on ventricular physiology and symptoms in patients with DLVOTO.

METHODS

We performed a pilot study in 15 patients (age 76+/-10 years, mean+/-S.D., 14 female) with symptoms of exercise intolerance (New York Heart Association, NYHA, class 2.7+/-0.5). All patients had normal resting left ventricular (LV) systolic function together with DLVOTO based on the presence of basal septal hypertrophy and the development of high outflow tract velocities on stress echocardiography. All were commenced on oral atenolol (mean dose 45+/-19 mg), but this could not be tolerated in four patients due to a deterioration in clinical status.

RESULTS

In the remaining 11 patients who could tolerate atenolol therapy, the rate pressure product was significantly lower (23%, P=0.028) and there was a marked reduction in LV outflow tract velocity (23%, P=0.001) following beta-blockade. Patient symptoms improved significantly following atenolol therapy, with a reduction in mean NYHA class from 2.8+/-0.4 to 1.5+/-0.5 (P<0.0001).

CONCLUSIONS

Beta-blockade may represent a beneficial therapeutic approach in selected patients with DLVOTO as identified by stress echocardiography.

Origin of symptoms in patients with cachexia with special reference to weakness and shortness of breath

Cachexia is a complication of many disorders. It is associated with an extremely poor prognosis and many symptoms. The wasting process affects particularly skeletal muscle causing extreme fatigue and weakness. In many underlying conditions associated with cachexia, the patient also suffers an often unexplained severe dyspnoea along with weakness, asthenia and exhaustion. There appears to be marked similarities in the cause of dyspnoea and fatigue between different cachectic conditions. Using the example of cardiac cachexia, this article reviews the evidence linking skeletal muscle reflex inputs to ventilatory control and exaggerated chemoreflex responses as candidates for the heightened perception of dyspnoea which cannot be explained by heart or lung dysfunction in many patients. Evidence is reviewed that similar processes may occur in other cachexias, especially those complicating cancer, AIDS, chronic liver disease, and chronic lung disease. Potential novel therapeutic strategies to combat these cachexia symptoms are reviewed.

Clinical implications of physiological changes in the aging heart

Elderly individuals experience a disproportionate burden from cardiovascular disease. Global changes in aging will have a significant impact on the future of medical practice. However, most physicians have little formal training in geriatric medicine and sometimes fail to distinguish disease states from normal aging. Increasingly, it is recognised that a sedentary lifestyle may be responsible for a large fraction of the so-called 'age-related' changes in the cardiovascular system. Nonetheless, well characterised changes do occur in most individuals with aging. Loss of myocytes with subsequent hypertrophy of the remaining cells is usually observed. Calcification involving the conduction and valvular apparatus is seen in most elderly individuals and may predispose to the common arrhythmias of old age. Age-related loss of arterial compliance contributes to isolated systolic hypertension and left ventricular hypertrophy. Despite these changes, for the majority of healthy older adults, cardiac output is well maintained in the basal state through use of the Frank-Starling principle, in the setting of reduced early diastolic filling. Myocardial relaxation is slowed in part due to age-related changes in the sarcoplasmic reticulum Ca2+ ATPase pump. Elevated blood levels of catecholamines contribute to desensitisation to noradrenergic stimulation and this is associated with an age-related decline in maximum achievable heart rate. Changes in the baroreceptor reflex function and decreased sodium conservation may predispose some individuals to orthostatic and postprandial hypotension. The aetiology of cardiovascular aging is under intense study. The most likely mechanisms involve the result of cumulative damage mediated through a variety of insults. Oxidative stress, non-enzymatic glycation, inflammation and changes in cardiovascular gene expression all seem to influence cardiovascular aging. The benefits of exercise continue to be discovered. Endurance-type training has been shown to have a dramatic impact on parameters of cardiovascular aging. Favourable effects are seen in maximum oxygen consumption, diastolic filling, relaxation and arterial stiffness. Some changes such as the maximum heart rate response do not appear to change with conditioning. Pharmacotherapy may afford the opportunity to influence the aging process. Drugs that can reduce age-associated arterial stiffness, cardiac fibrosis and ventricular hypertrophy should prove useful. Antioxidants continue to be a topic of great interest and require more study. Despite some well described changes with aging, most elderly individuals maintain the opportunity for improved cardiovascular function through conditioning. Early recognition and treatment of diseases that are distinguishable from normal aging, including hypertension and atherosclerosis, together with preventive efforts, should reduce the predicted trends in cardiovascular morbidity and mortality among the aged.