Exercise-induced intra-ventricular gradients as a frequent potential cause of myocardial ischemia in cardiac syndrome X patients

Exercise-Induced Intraventricular Gradients As a Potential Cause of Sudden Cardiac Death

A 16-year-old boy reported an episode of dizziness related to intense training six months before an episode of aborted sudden death. The screening required for competitive sports practice was normal. There were no personal or familial antecedents of sudden death or heart disease. After winning a triathlon competition, he experienced a cardiac arrest episode. He received defibrillation with the return of spontaneous circulation. A medical evaluation that included electrocardiogram (ECG) and echocardiogram had normal results. A complete study including cardiac MRI, coronary CT angiography, a genetic study for heart disease, the flecainide test, and a stress echocardiogram with ergometrine was done, and all results were normal. During a Holter ECG and exercise stress echo, isolated premature ventricular complexes were detected. During the effort treadmill stress echocardiogram, the athlete developed a significant intraventricular obstruction with an end-systolic peak, without systolic anterior movement of the mitral valve, which disappeared in the first minute of the recovery. We highlight the possible cause-effect relation between the events.

Exercise stress echocardiography: Where are we now?

Exercise stress echocardiography (ESE) is a widely used diagnostic test in cardiology departments. ESE is mainly used to study patients with coronary artery disease; however, it has increasingly been used in other clinical scenarios including valve pathology, congenital heart disease, hypertrophic and dilated cardiomyopathies, athlete evaluations, diastolic function evaluation, and pulmonary circulation study. In our laboratories, we use an established methodology in which cardiac function is evaluated while exercising on a treadmill. After completing the exercise regimen, patients remain in a standing position or lie down on the left lateral decubitus, depending on the clinical questions to be answered for further evaluation. This method increases the quality and quantity of information obtained. Here, we present the various methods of exercise stress echocardiography and our experience in many clinical arenas in detail. We also present alternatives to ESE that may be used and their advantages and disadvantages. We review recent advances in ESE and future directions for this established method in the study of cardiac patients and underline the advantage of using a diagnostic tool that is radiation-free.

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.

Hypertrophic cardiomyopathy: genotype-positive, phenotype-"almost" negative. Diagnostic role of exercise in provocation of left ventricular outflow tract gradient

It has been proposed to use exercise stress echocardiography in the upright position with left ventricular outflow tract gradient monitoring both during and after exercise as a marker of genotype-positive/phenotype negative hypertrophic cardiomyopathy (HCM). Doppler measurement of gradient has been a very helpful and diagnostic examination in several subgroups of subjects (especially in young persons, athletes). Recently, many noninvasive (bio)markers have been found to be very helpful in screening patients suspected of HCM before full expression of phenotype.

Need for a standardized protocol for stress echocardiography in provoking subaortic and valvular gradient in various cardiac conditions

(Semi) supine exercise testing has an established role in the evaluation of patients with valvular heart disease and can help clinical decision making. Stress echocardiography has the advantages of its wide availability, low cost, and versatility for the assessment of disease severity. However, exercise-induced changes in valve hemodynamics, left ventricular outflow obstruction and pulmonary artery pressure depended on load variation. Changing position from supine to upright rapidly decreases load conditions for the ventricles. Therefore several cardiac centers have proposed exercise stress echocardiography in the upright position with gradient monitoring sometimes also in post-exercise recovery. Doppler measurement of subaortic gradient has been a very helpful and informative examination in several heart diseases (especially in hypertrophic cardiomyopathy, valve heart diseases, prosthesis dysfunction).

Clinical applications of exercise stress echocardiography in the treadmill with upright evaluation during and after exercise

Exercise stress echocardiography is the most frequently used stress test in our laboratory. Exercise echocardiography is used mainly in the study of patients with coronary artery disease. However, the technique is increasingly being used to study other diseases. In our centre, we use an original methodology, published by us in 2000, in which we evaluate heart function during exercise in the treadmill. After the exercise, patients are maintained in orthostatic position when appropriate or lying down in left lateral decubitus for further evaluation. Since this method seems to increase the quality and the quantity of information obtained in so many clinical arenas, we now present a detailed review of this methodology and its applications.

Exercise-induced intraventricular obstruction in a child with near syncope and chest pain during exercise

We report the case of a 10-year-old girl with two episodes of light-headedness and chest pain during exercise. She had an unremarkable clinical record, physical examination, ECG, and echocardiogram. Noninvasive ischemia tests were positive, but coronary angiography was normal. Exercise stress echocardiogram revealed an exercise-induced intra-left-ventricular obstruction with a peak gradient of 78 mmHg and replicated her symptoms. After starting beta-blocker therapy her clinical status improved and no residual obstruction was detected. The authors review this unsuspected clinical condition, seldom reported in the adult population and, to our knowledge, never before in a child.

Stress-induced intraventricular gradients in symptomatic athletes during upright exercise continuous wave Doppler echocardiography

The development of significant intraventricular gradients (IVGs) during exercise has been described anecdotally in athletes. However, the prevalence and clinical effect of this observation are unclear. In addition, the most appropriate exercise technique (upright vs semisupine) for eliciting IVGs also remains unknown. The present study had 2 main aims: (1) to identify the prevalence of exercise IVGs in athletes whose preparticipation cardiovascular screening result for sports practice, according to the European Society of Cardiology guidelines, was positive; and (2) to evaluate the influence of performing exercise echocardiography, as described, on the detection of IVGs. We enrolled 139 consecutive athletes (135 amateurs and 4 professionals, mean age 22 ± 9.9 years; 30 women) who underwent treadmill exercise echocardiography. In each athlete, the IVG was evaluated by continuous wave Doppler during 5 conditions: left lateral decubitus at rest; upright at rest; upright at peak treadmill exercise; upright in the recovery phase; and left lateral decubitus in the recovery phase. All patients had normokinetic regional wall motion at rest and during exercise. According to the detection of IVG during treadmill echocardiography (IVG was considered significant if >30 mm Hg at rest or >50 mm Hg during/after exercise), 2 groups were identified: a group (n = 52), with significant IVG and a group (n = 87) without significant IVG. The IVG was greater in the upright position, both at rest (only 2 athletes from group with IVG) and after exercise (52 athletes, all from group with IVG). The IVG was lower in the recovery phase in the left lateral decubitus position (55 ± 15 mm Hg in 30 athletes, all from group with IVG) than in the upright position in the recovery phase (95 ± 35 mm Hg in 52 athletes, all from group with IVG) and at peak exercise (66 ± 24 mm Hg in 41 athletes from group with IVG). We observed systolic anterior movement of the mitral valve in 33 of the 52 athletes in the group with IVG and in none of the athletes in the group without IVG. In conclusion, in athletes, exercise-induced symptoms and/or ischemia-like electrocardiographic signs are often associated with significant IVG, developing in the absence of wall motion abnormalities. IVG was more evident during post-treadmill upright imaging.

Efficacy of beta-blocker therapy in symptomatic athletes with exercise-induced intra-ventricular gradients

Background

Upright exercise stress echocardiography (SE) induces significant intraventricular gradient (IVG) and systolic anterior motion (SAM) in a large proportion of symptomatic athletes, who may therefore benefit from a negative inotropic therapy.

The purpose of the present study was to assess the effect of chronic oral β blocker therapy on the occurrence of exercise-induced IVG and mitral valve SAM, in symptomatic athletes.

Methods

We enrolled 35 symptomatic athletes (age = 23 ± 11 years) with IVG (>30 mmHg) during SE off therapy. All repeated SE on chronic oral beta-blocker therapy (atenolol up to 50 mg, bisoprolol up to 10 mg, or metoprolol up to 100 mg daily according to physician-driven choice).

Results

On therapy, there was during SE a reduction in IVG (35 off vs 17 on beta blocker, p < 0.01), decrease of IVG (102 ± 34 mmHg off vs 69 ± 24 mmHg on beta blocker, p < 0.01), peak heart rate (178 ± 15 bpm off vs 157 ± 9 bpm on beta blocker), SAM (24 off vs 9 on beta blocker, p < 0.001), symptoms during SE (17 off vs 2 on beta blocker p < 0.001), ST segment depression (13 off vs 2 on beta blocker, p < 0.001).

Conclusions

In athletes with positive screening on medical evaluation for sports practice and IVG on exertion, treatment with oral beta blockers improved symptoms in the large majority of patients. Symptomatic benefit was mirrored by objective evidence of improvement of echocardiographic signs of obstruction (IVG and SAM) and reduction of ischemia-like electrocardiographic changes.

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.

Definitions and incidence of cardiac syndrome X: review and analysis of clinical data

There is no consensus regarding the definition of cardiac syndrome X (CSX). We systematically reviewed recent literature using a standardized search strategy. We included 57 articles. A total of 47 studies mentioned a male/female distribution. A meta-analysis yielded a pooled proportion of females of 0.56 (n = 1,934 patients, with 95% confidence interval: 0.54-0.59). As much as 9 inclusion criteria and 43 exclusion criteria were found in the 57 articles. Applying these criteria to a population with normal coronary angiograms and treated in 1 year at a general hospital, the attributable CSX incidence varied between 3 and 11%. The many inclusion and exclusion criteria result in a wide range of definitions of CSX and these have large effects on the incidence. This shows the need for a generally accepted definition of CSX.