Postprandial Hemodynamics in Hypertrophic Cardiomyopathy.

OBJECTIVES: Prior analysis at our institution found that patients with hypertrophic cardiomyopathy (HCM) who experience postprandial symptoms (PPS) are more likely to have resting left ventricular outflow tract (LVOT) obstruction and reduced quality of life. Our objective was to determine whether PPS in patients with HCM vs healthy subjects occur as a result of measurable hemodynamic alterations in the postprandial hemodynamic response. METHODS: We conducted a prospective cross-sectional study examining 45 patients with HCM and 10 controls who underwent fasting and postprandial 2-dimensional Doppler echocardiography. Postprandial echocardiographic measurements were obtained at symptom onset or 30 minutes after consumption of a standardized meal, whichever occurred first. RESULTS: The HCM population included 18 (40%) patients with PPS and 27 (60%) without PPS. Compared to controls, mean resting peak LVOT gradient was 23.4 ± 17.6 mmHg in HCM patients with PPS and 25.1 ± 33.1 mmHg in those without PPS (P = 0.10). The mean change in peak LVOT gradient after a meal was 0.7 ± 1.1 mmHg for controls, 5.0 ± 8.3 mmHg for HCM patients with PPS, and 1.5 ± 18.2 mmHg for HCM patients without PPS (P = 0.64). CONCLUSION: Although the ability to provoke an increased LVOT gradient with a postprandial, upright exercise study protocol was recently reported, the current study suggests that a resting, supine, postprandial protocol does not elicit evidence of LVOT obstruction. Therefore, future investigations should consider whether simply performing an upright postprandial study in HCM patients with PPS will provide evidence of dynamic LVOT or if the addition of an exercise component is necessary.

Potential role of Reynolds number in resolving Doppler- and catheter-based transvalvular gradient discrepancies in aortic stenosis.

BACKGROUND AND AIM OF THE STUDY: Discrepancies in mean transvalvular gradient have been observed between Doppler echocardiography and catheter-based techniques in the assessment of aortic stenosis (AS). The Reynolds number (RE) has been shown to influence Doppler-derived gradients, and may be useful in resolving Doppler- and catheter-based gradient discrepancies in AS. The study aim was to assess the influence of the RE on such discrepancies. METHODS: A pulsatile in-vitro heart model using a bioprosthetic aortic valve with leaflets sutured together was used to simulate AS. Simultaneous gradients were measured using Doppler echocardiography and high-fidelity catheters while the RE was varied, by testing solutions of different density and viscosity across a range of cardiac outputs. RESULTS: The echocardiographic and catheter-derived mean gradient (MG) values were correlated (r = 0.89; p < 0.0001); however, significant differences in the MG were observed across hemodynamic states. A direct linear relationship was identified between RE and the absolute difference in MG measured using the two techniques (r = 0.94, p < 0.0001). Relative to catheter-based measurements, the MG was underestimated by Doppler (range: 13-16 mmHg) at low RE (median 6,999) and overestimated (7-33 mmHg) at high RE (median 34,268). However, agreement between catheter- and Doppler-derived gradients was within 5 mmHg at intermediate RE (median 17,284) (p < 0.0001). CONCLUSION: The underestimation of Doppler-derived MGs at low RE relative to catheter-based measurements may be due to an exclusion of viscous friction from the simplified Bernoulli equation, while the overestimation of Doppler-derived MGs at high RE may be due to a pressure recovery effect. However, within an intermediate range of RE, where the effects of viscous and inertial forces are balanced, the agreement between catheter- and Doppler-derived gradients was excellent.

Relation Between Temperature Extremes and Symptom Exacerbation in Patients With Hypertrophic Cardiomyopathy.

Warm temperatures induce peripheral vasodilation, decrease afterload, and may concurrently increase the left ventricular outflow tract (LVOT) gradient. We aimed to assess the impact of subjective ambient temperature on hypertrophic cardiomyopathy (HC) symptoms and determine whether they were associated with LVOT gradient, patient quality of life (QOL), and risk of sudden cardiac death (SCD). We identified consecutive patients with HC presenting to a tertiary referral center. Of the 173 patients in the study, 143 (83%) had HC symptoms, with ambient temperature change worsening symptoms for 72 patients (50%). Symptom exacerbation occurred only with heat for 57 (79%), whereas symptoms were exacerbated with cold only or with cold and heat equally for 15 (21%). Patients affected by any temperature exacerbation more commonly were women (p = 0.009), had a lower QOL (p = 0.04), had a family history of HC (p = 0.007), or underwent myectomy (p = 0.01). A greater proportion of patients with heat-only exacerbation had a family history of HC (p = 0.005) and SCD (p = 0.05). The presence of an LVOT gradient either at rest or with provocation was similar in all groups. In conclusion, although no appreciable difference in LVOT gradients were observed between patient groups, approximately half of the patients with HC reporting symptoms at baseline noted worsening of symptoms with temperature changes, with >75% describing heat-induced symptom exacerbation. Furthermore, affected patients more frequently were women, underwent surgical intervention and device implantation, and had an overall lower QOL.

Effect of Continued Cardiac Resynchronization Therapy on Ventricular Arrhythmias After Left Ventricular Assist Device Implantation.

Cardiac resynchronization therapy (CRT) reduces ventricular arrhythmia (VA) burden in some patients with heart failure, but its effect after left ventricular assist device (LVAD) implantation is unknown. We compared VA burden in patients with CRT devices in situ who underwent LVAD implantation and continued CRT (n = 39) to those who had CRT turned off before discharge (n = 26). Implantable cardioverter-defibrillator (ICD) shocks were significantly reduced in patients with continued CRT (1.5 ± 2.7 shocks per patient vs 5.5 ± 9.3 with CRT off, p = 0.014). There was a nonsignificant reduction in cumulative VA episodes per patient with CRT continued at discharge (42 ± 105 VA per patient vs 82 ± 198 with CRT off, p = 0.29). On-treatment analysis by whether CRT was on or off identified a significantly lower burden of VA (17 ± 1 per patient-year CRT on vs 37 ± 1 per patient-year CRT off, p <0.0001) and ICD shocks (1.2 ± 0.3 per patient-year CRT on vs 1.7 ± 0.3 per patient-year CRT off, p = 0.018). In conclusion, continued CRT is associated with significantly reduced ICD shocks and VA burden after LVAD implantation.

Novel ECG criteria for right ventricular systolic dysfunction in patients with right bundle branch block.

BACKGROUND: Altered hemodynamics of a failing right ventricle (RV) may place stress on the right bundle branch and Purkinje network, which may be evident as conduction delay on surface electrocardiogram (ECG). We hypothesized that prolonged R' duration in lead V1 would be an indicator of RV dysfunction in patients with RBBB. METHODS: The Mayo Clinic Arizona echocardiography database was reviewed from 2007 to 2009 to identify patients with RV dysfunction and coexistent right bundle branch block (RBBB). Specific ECG features of RBBB were compared between the RV dysfunction cohort and a randomly selected control population. Features found to be predictive of RV dysfunction were then tested on 100 consecutive patients with RBBB on ECG between January and June 2010. RESULTS: In lead V1, the QRS duration was longer in the RV dysfunction cohort (164 ± 22 ms) compared to controls (148 ± 12 ms), predominantly due to R' prolongation (117 ± 27 ms vs. 87 ± 13 ms, p<.001). Retrospective analysis suggested that V1 R' duration ≥ 100 ms may be 82.3% specific for the presence of RV systolic dysfunction. When applied prospectively, V1 R' duration ≥ 100 ms yielded sensitivity and specificity of 39.0% and 82.9% respectively for detection of abnormal RV systolic function with a positive predictive value of 76.7%. CONCLUSION: Lead V1 R' duration ≥ 100 ms is predictive of RV systolic dysfunction in patients with RBBB.

Advances in management of premature ventricular contractions.

Premature ventricular complexes (PVCs) are a common occurrence in clinical practice. The clinical presentation may range from asymptomatic to left ventricular (LV) dysfunction with congestive heart failure. The decision to suppress PVCs is largely based on the presence of symptoms, interference with other therapy (e.g., cardiac resynchronization therapy), or suspicion of PVC-mediated cardiomyopathy. Catheter ablation has emerged as a safe and effective option for the treatment of frequent PVCs. Careful attention to PVC characteristics on surface electrocardiogram has proven useful for the initial localization of the ectopic focus, which may then serve as a guide to procedural planning. The point of interest is often identified with activation mapping, and the ablation site can be further defined with pace mapping techniques. Clinical experience with PVC ablation has been successful in ≥80 % of cases, and the literature reports multiple cases of marked improvement in LV function after eradicating the culprit ectopic focus in patients with PVC-mediated cardiomyopathy.

Significance of postprandial symptom exacerbation in hypertrophic cardiomyopathy.

Patients with hypertrophic cardiomyopathy (HC) can experience exacerbation of exertional symptoms after a meal. The present study was designed to determine the prevalence and clinical correlates of postprandial symptom exacerbation (PPSE) in patients with HC. The records of 558 patients with HC and PPSE data who had undergone echocardiography at our institution from 2002 to 2006 were reviewed. Continuous-wave Doppler velocities were used to determine the left ventricular outflow tract gradient. Left ventricular filling was assessed using transmitral velocity curves. The Minnesota Living With Heart Failure questionnaire was administered to measure symptom limitations. A multivariate regression model was developed to determine the independent correlates with PPSE. Of the 558 patients whose records were reviewed, 189 (33.8%) had PPSE. The patients with PPSE were more likely to experience New York Heart Association class III/IV dyspnea or presyncope. PPSE was associated with greater resting outflow gradients and lower perceived quality of life. In conclusion, patients presenting with severe postprandial symptoms and reduced quality of life should be carefully evaluated for the presence of dynamic left ventricular outflow tract obstruction.