Dobutamine stress echocardiography in hypertrophic cardiomyopathy

[Hypertrophic cardiomyopathy]

Hypertrophic cardiomyopathy is the most common genetically determined cardiac disease with a prevalence of 0.2-0.6%. The most important pathophysiological phenomenon is dynamic obstruction predominantly of the left ventricular outflow tract in 70% of the patients. Clinical symptoms (e.g. dyspnea, angina pectoris and syncope) are extremely variable depending on changes in preload and afterload and an increased risk of sudden cardiac death particularly in younger patients. The diagnostic measures should be carried out with respect to a prognostic and symptomatic treatment with implantation of an implantable cardioverter defibrillator (ICD) in cases of increased risk of sudden cardiac death. When medication treatment fails, first-line treatment consists of septal ablation and surgical myectomy as a supplementary measure, depending on the underlying morphology and experience of the surgeon.

Prognostic role of stress echocardiography in hypertrophic cardiomyopathy: The International Stress Echo Registry

BACKGROUND

Stress echo (SE) may have a role in the outcome in patients with hypertrophic cardiomyopathy (HCM).

OBJECTIVES

The aim was to assess the prognostic value of SE in a retrospective multicenter study in HCM.

METHODS

We enrolled 706 HCM patients. The employed stress was exercise (n=608) and/or vasodilator (n=146, dipyridamole in 98 and adenosine in 48). We defined SE positivity according to clinical/hemodynamic criteria including: symptoms (all stress modalities), exercise-induced hypotension (failure to increase or fall >20mmHg, exercise) and exercise-induced left ventricular outflow tract obstruction (left ventricular outflow tract obstruction >50mmHg); and ischemic criteria, such as new wall motion abnormalities (new wall motion abnormality) and/or reduction of coronary flow reserve velocity (CFVR≤2.0) on left anterior descending coronary artery with vasodilator stress assessed in 116 patients. All patients completed the clinical follow-up.

RESULTS

Positive SE showed more frequently CFVR reduction, exercise-induced hypotension, left ventricular outflow tract obstruction, and symptoms (38, 23, 20 and 15% respectively), but new wall motion abnormality only in 6%. During a median follow-up of 49months 180 events were observed, including 40 deaths. Clinical/hemodynamic criteria did not predict outcome (X2 0.599, p=0.598), whereas ischemia-related SE criteria (X2: 111.120, p<0.0001) was significantly related to outcome. Similarly, mortality was predicted with SE ischemic-criteria (X2 16.645, p<0.0001).

CONCLUSIONS

SE has an important prognostic significance in HCM patients, with ischemia-related end-points showing greater predictive accuracy than hemodynamic endpoints. New wall motion abnormalities and impairment of CFVR should be specifically included in SE protocols for HCM.

Left ventricular outflow tract obstruction caused by massive mitral annular calcification in a patient with hypertensive heart disease

Mitral annular calcification (MAC) is frequently observed, but it rarely causes left ventricular outflow tract (LVOT) obstruction (LVOTO). An 83-year-old woman with hypertension, diabetes, and dyslipidemia was admitted to our hospital because of exertional dyspnea. She was diagnosed with hypertensive heart disease. Her symptoms were exacerbated by exertion, and she had no symptoms at rest. Transthoracic echocardiography showed massive posterior MAC, a sigmoid septum, and LVOTO, with a peak gradient of 15.4 mmHg at rest. Systolic anterior motion of the anterior mitral leaflet was not found. Moreover, the LVOT gradient in the stress condition was evaluated, and an increased LVOT gradient (47.3 mmHg) and chest discomfort was noted after 20 μg/kg/min of dobutamine was administered and the Valsalva maneuver was used. Hence, the patient was diagnosed with latent LVOTO. Interestingly, the distance between the septal wall, which was protruding into the left ventricular cavity, and the mitral valve coaptation, which was pushed up by the posterior MAC, had become closer, causing dynamic LVOTO. Since it is difficult to treat LVOTO with medication, ultimately, septal myectomy and mitral valve replacement were performed, which improved her symptoms. Evaluating the LVOT pressure gradient in stress condition is important in patients with MAC. .

Cerebral vasospasm and concurrent left ventricular outflow tract obstruction: requirement for modification of hyperdynamic therapy regimen

BACKGROUND

Medical treatment of arterial vasospasm following aneurysmal subarachnoid hemorrhage (SAH) generally consists of triple H therapy, which frequently relies on inotropic agents in order to increase cardiac output (CO). Patients with concurrent left ventricular outflow tract (LVOT) obstruction may have paradoxical decreases in CO following administration of inotropic pressors, placing them at significant risk for cerebral ischemia and stroke.

METHODS

The clinical courses of two patients with SAH-induced arterial vasospasm and underlying left ventricular outflow obstruction are reported. Both patients had hypotension and low cardiac output that were refractory to medical management with triple H therapy. Echocardiography in both patients demonstrated LVOT obstruction secondary to hypertrophic obstructive cardiomyopathy (HOCM).

RESULTS

Intervention in both patients included discontinuation of inotropic agents and maintenance of hypervolemia to a target pulmonary capillary wedge pressure range, resulting in improved cardiac output and mean arterial pressure.

CONCLUSION

Medical treatment for cerebral vasospasm with inotropic pressor agents may result in paradoxical decreases in hemodynamic parameters and cerebral perfusion in patients with LVOT obstruction. While HOCM is the most likely structural abnormality to cause this phenomenon, it can be induced by several physiological conditions encountered in the neurocritical care setting. Modifications in triple H therapy regimens may be required in order to optimize cerebral perfusion and prevent cerebral ischemia and stroke in these patients.

Echocardiography in patients with hypertrophic cardiomyopathy: usefulness of old and new techniques in the diagnosis and pathophysiological assessment

Hypertrophic cardiomyopathy (HCM) is one of the most common inherited cardiomyopathy. The identification of patients with HCM is sometimes still a challenge. Moreover, the pathophysiology of the disease is complex because of left ventricular hyper-contractile state, diastolic dysfunction, ischemia and obstruction which can be coexistent in the same patient. In this review, we discuss the current and emerging echocardiographic methodology that can help physicians in the correct diagnostic and pathophysiological assessment of patients with HCM.

Microvascular dysfunction, myocardial ischemia, and progression to heart failure in patients with hypertrophic cardiomyopathy

Microvascular dysfunction can be demonstrated in most patients with hypertrophic cardiomyopathy (HCM), both in the hypertrophied and nonhypertrophied myocardial walls, mostly due to intimal and medial hyperplasia of the intramural coronary arteries and subsequent lumen reduction. As a consequence, regional myocardial ischemia may be triggered by exercise, increased heart rate, or arrhythmias, in areas which are unable to increase myocardial blood flow. In patients with HCM, microvascular dysfunction leading to severe myocardial hypoperfusion during maximal hyperemia represents a strong predictor of unfavorable outcome, left ventricular remodeling with progressive wall thinning, left ventricular dysfunction, and heart failure. Accurate quantitative assessment of microvascular dysfunction and myocardial ischemia is not easily feasible in clinical practice. Although signs of inducible myocardial ischemia may be detected by electrocardiogram, echocardiography, or myocardial scintigraphy, the vasodilator response to dipyridamole by positron emission tomography is considered the method of choice for the assessment of maximal regional and global flow. Cardiac magnetic resonance provides further information, by late gadolinium enhancement (LGE), which may show areas where replacement fibrosis has occurred following microvascular ischemia and focal necrosis. LGE areas colocalize with severe regional microvascular dysfunction, are associated with increased prevalence of ventricular arrhythmias, and show more extensive distribution in the late stages of the disease, when heart failure is the dominant feature. The present review aims to provide a concise overview of the available evidence of microvascular dysfunction and ischemia eventually leading to disease progression and heart failure in HCM patients.

Prognostic significance of exercise induced arrhythmias and echocardiographic variables in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HC) often presents with exercise-induced symptoms, including arrhythmias and sudden death. The investigators prospectively studied whether exercise testing is associated with immediate complications and if stress-induced arrhythmias and echocardiographic variables are associated with long-term adverse outcomes. Exercise echocardiography with 6-channel continuous monitoring for arrhythmias was performed in consecutive patients with HC clinically referred for the test. End points included death, myocardial infarction, revascularization, stroke, atrial fibrillation, ventricular tachycardia, and myectomy. Of 86 patients with HC (mean age 56.6 +/- 16.1 years) who underwent exercise echocardiography, arrhythmias occurred in 39 (45%), including 23 (27%) with premature atrial contractions, 2 (2%) with atrial fibrillation, 28 (33%) with premature ventricular contractions (16 also had atrial arrhythmias), and 1 (1.2%) with nonsustained ventricular tachycardia (hemodynamically stable). During a follow-up of 2.6 +/- 2.8 years, major events occurred in 11 patients (3 deaths, 5 revascularizations, 3 strokes). In addition, 12 patients developed atrial fibrillation, 6 developed nonsustained ventricular tachycardia, and 13 underwent myectomies. Variables associated with major events included hypertension, male gender, and worsening wall motion score index with exercise; increased exercise duration was associated with fewer events. ST-T changes on baseline electrocardiography and premature ventricular contractions were associated with atrial fibrillation risk. In conclusion, in this cohort of patients with HC, exercise testing was safe. Test results were associated with risk for adverse events.

Left ventricular systolic function during stress echocardiography exercise in subjects with asymptomatic hereditary hemochromatosis

There is no information available on left ventricular (LV) systolic function and the response to stress echocardiography in asymptomatic subjects with hereditary hemochromatosis (HH). To evaluate this topic, 43 asymptomatic subjects with HH homozygous for the C282Y HFE gene mutation (22 untreated subjects [group A] and 21 long-term treated subjects [group B]) were compared with 21 age- and gender-matched normal volunteers negative for HFE mutations. Contractile reserve, as a measure of LV systolic function, was assessed using continuous echocardiographic imaging and electrocardiography during supine bicycle exercise. Nineteen subjects in group A had repeat tests after 6 months of induction phlebotomy therapy to assess the effect of iron removal. Exercise performance and hemodynamic variables of supine bicycle exercise were comparable between subjects with HH and controls. LV contractile reserve of asymptomatic subjects with HH was not impaired at either a 75-W submaximal exercise level (mean +/- SD difference in ejection fraction from baseline 13.8 +/- 6.2%, 11.5 +/- 6.8%, and 13.4 +/- 7.8% in groups A, B, and C, respectively; p = NS for all by analysis of variance) or at peak exercise (difference in ejection fraction from baseline 18.9 +/- 6.9%, 18.4 +/- 7.8%, and 20.3 +/- 8.1% in groups A, B, and C, respectively; p = NS for all by analysis of variance). However, the incidence of abnormal ischemic stress electrocardiographic responses was more frequent in subjects with HH as a whole (33%) compared with normal subjects (10%). Stress imaging revealed no regional wall motion abnormalities, suggesting that these were false-positive results. Iron removal by induction phlebotomy did not affect stress echocardiographic performance. In conclusion, LV systolic function during exercise in asymptomatic subjects with HH is preserved, and 6-month induction phlebotomy does not affect stress echocardiographic performance.