Reversal of Inappropriate Peripheral Vascular Responses in Hypertrophic Cardiomyopathy

Diagnostic yield of head-up tilt table test in hypertrophic cardiomyopathy and unexplained syncope: the knot does not seem to be unraveling

BACKGROUND

Conflicting results have been published considering the diagnostic performance of head-up tilt test (HUTT) in patients with hypertrophic cardiomyopathy (HCM). We aimed to conduct a meta-analysis to evaluate the diagnostic value of HUTT in the evaluation of unexplained syncope in patients with HCM.

METHODS

We performed a structured systematic database search using the following keywords: hypertrophic cardiomyopathy, syncope, unexplained syncope, head-up tilt test, tilt table test, tilt testing, orthostatic stress, autonomic function, autonomic response. Studies in which the HUTT was used to define autonomic dysfunction in patients with syncope at baseline or without syncope were included in the final analysis.

RESULTS

A total of 252 HCM patients from 6 studies (159 patients without a history of syncope and 93 with a history of syncope, respectively) were evaluated. HUTT was positive in 50 (19.84%) of 252 patients (in 21 of 93 patients (22.58%) with a history of syncope and in 29 of 159 patients (18.24%) without a history of syncope, respectively). The pooled total sensitivity and specificity of the HUTT for detecting syncope were 22.1% (14.8-35.1%) and 83.6% (73.2-91.6%), respectively. The summary receiver operator curve showed that HUTT had an only modest discriminative ability for syncope with an area under the curve value of 0.565 (0.246-0.794).

CONCLUSION

Although HUTT has significant limitations in diagnosis of unexplained syncope in patients with HCM, it may still be used to determine hypotensive susceptibility. Other autonomic tests can be used in diagnostic workflow in this population.

Transcatheter mitral valve repair for the treatment of severe mitral regurgitation and exertional pre-syncope in a patient with non-obstructive hypertrophic cardiomyopathy: a case report

Background

Hypertrophic cardiomyopathy (HCM) has a complex pathophysiology and heterogeneous phenotypic expression. In obstructive HCM with significant mitral regurgitation (MR), MitraClip device implantation reduces MR severity and symptoms. There are no data regarding MitraClip implantation in patients with non-obstructive HCM and significant MR.

Case summary

A 78-year-old woman with non-obstructive HCM and significant functional MR (3+) was admitted to our centre for dyspnoea and episodes of pre-syncope under light stress. Transthoracic and transoesophageal echocardiography showed a normal left ventricular ejection fraction and normal right heart pressures, an inverted mitral filling pattern, and a central prevalent jet (A2-P2 origin) of MR. Exercise echocardiography performed to verify exercise tolerance was interrupted at the 50-W stage due to severe hypotension and pre-syncope. After transcatheter edge-to-edge repair using the MitraClip system, the patient exhibited a reduction in MR Grade from 3+ to 1+. Follow-up up to 1-year post-procedure revealed noticeable improvements in exercise tolerance and symptoms. There were no further episodes of pre-syncope.

Discussion

In non-obstructive HCM, the pathophysiological role of MR in symptom generation is unknown. In this patient, we speculated that significant MR contributed to the mechanisms responsible for severe hypotension and pre-syncope during exercise. A reduction in MR after MitraClip implantation was associated with symptomatic improvements. Our findings further highlight the potential utility of the exercise stress test in therapeutic decision-making for patients with non-obstructive HCM and MR.

Biventricular pacemaker therapy improves exercise capacity in patients with non-obstructive hypertrophic cardiomyopathy via augmented diastolic filling on exercise

AIMS

Treatment options for patients with non-obstructive hypertrophic cardiomyopathy (HCM) are limited. We sought to determine whether biventricular (BiV) pacing improves exercise capacity in HCM patients, and whether this is via augmented diastolic filling.

METHODS AND RESULTS

Thirty-one patients with symptomatic non-obstructive HCM were enrolled. Following device implantation, patients underwent detailed assessment of exercise diastolic filling using radionuclide ventriculography in BiV and sham pacing modes. Patients then entered an 8-month crossover study of BiV and sham pacing in random order, to assess the effect on exercise capacity [peak oxygen consumption (VO₂ )]. Patients were grouped on pre-specified analysis according to whether left ventricular end-diastolic volume increased (+LVEDV) or was unchanged/decreased (-LVEDV) with exercise at baseline. Twenty-nine patients (20 male, mean age 55 years) completed the study. There were 14 +LVEDV patients and 15 -LVEDV patients. Baseline peak VO₂ was lower in -LVEDV patients vs. +LVEDV patients (16.2 ± 0.9 vs. 19.9 ± 1.1 mL/kg/min, P = 0.04). BiV pacing significantly increased exercise ΔLVEDV (P = 0.004) and Δstroke volume (P = 0.008) in -LVEDV patients, but not in +LVEDV patients. Left ventricular ejection fraction and end-systolic elastance did not increase with BiV pacing in either group. This translated into significantly greater improvements in exercise capacity (peak VO₂  + 1.4 mL/kg/min, P = 0.03) and quality of life scores (P = 0.02) in -LVEDV patients during the crossover study. There was no effect on left ventricular mechanical dyssynchrony in either group.

CONCLUSION

Symptomatic patients with non-obstructive HCM may benefit from BiV pacing via augmentation of diastolic filling on exercise rather than contractile improvement. This may be due to relief of diastolic ventricular interaction.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov NCT00504647.

Head-Up Tilt Test in Risk Stratification of Patients with Hypertrophic Cardiomyopathy

Conflicting results have been published considering the role of head-up tilt test (HUTT) positivity as a prognostic factor in patients with hypertrophic cardiomyopathy (HCM). The relationship between HCM patients' genotype and their HUTT results has not been previously reported. The aim of this study was to evaluate patients with HCM and their HUTT results in regard to its value for outcome prediction and to investigate the relation of patients' genotype and their HUTT results. Seventy-four (51 ± 15 years; 42% women; median follow-up 72 months) HCM patients were divided into two groups based on their HUTT results and were retrospectively analyzed. In 67 (90.5%) subjects included in the analysis, next-generation sequencing-based genomic testing was performed. A composite end point of unexplained syncope, heart failure hospitalization, and death was defined. A total of 14 patients (18.9%) had positive HUTT (HUTT+), whereas 60 (81.1%) had negative HUTT (HUTT-). Except for the New York Heart Association functional class ( p  = 0.01), both groups had similar characteristics. Positive genotype was evenly distributed between the two groups. Composite end point occurred in 5 patients (35.7%) in HUTT+ group versus 14 (23.3%) patients in HUTT- group ( p  = 0.33). We did not find a relationship between HUTT results and long-term outcome. We found no association between HUTT results and genotype.

Update on hypertrophic cardiomyopathy and a guide to the guidelines

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiovascular disorder, affecting 1 in 500 individuals worldwide. Existing epidemiological studies might have underestimated the prevalence of HCM, however, owing to limited inclusion of individuals with early, incomplete phenotypic expression. Clinical manifestations of HCM include diastolic dysfunction, left ventricular outflow tract obstruction, ischaemia, atrial fibrillation, abnormal vascular responses and, in 5% of patients, progression to a 'burnt-out' phase characterized by systolic impairment. Disease-related mortality is most often attributable to sudden cardiac death, heart failure, and embolic stroke. The majority of individuals with HCM, however, have normal or near-normal life expectancy, owing in part to contemporary management strategies including family screening, risk stratification, thromboembolic prophylaxis, and implantation of cardioverter-defibrillators. The clinical guidelines for HCM issued by the ACC Foundation/AHA and the ESC facilitate evaluation and management of the disease. In this Review, we aim to assist clinicians in navigating the guidelines by highlighting important updates, current gaps in knowledge, differences in the recommendations, and challenges in implementing them, including aids and pitfalls in clinical and pathological evaluation. We also discuss the advances in genetics, imaging, and molecular research that will underpin future developments in diagnosis and therapy for HCM.

Effects of lifestyle changes and high-dose β-blocker therapy on exercise capacity in children, adolescents, and young adults with hypertrophic cardiomyopathy

AIM

The use of β-blocker therapy in asymptomatic patients with hypertrophic cardiomyopathy is controversial. This study evaluates the effect of lifestyle changes and high-dose β-blocker therapy on their exercise capacity.

METHODS AND RESULTS

A total of 29 consecutive newly diagnosed asymptomatic patients with familial hypertrophic cardiomyopathy, median age 15 years (range 7-25), were recruited. In all, 16 patients with risk factors for sudden death were treated with propranolol if no contraindications, or equivalent doses of metoprolol; 13 with no risk factors were randomised to metoprolol or no active treatment. Thus, there were three treatment groups, non-selective β-blockade (n=10, propranolol 4.0-11.6 mg/kg/day), selective β-blockade (n=9, metoprolol 2.7-5.9 mg/kg/day), and randomised controls (n=10). All were given recommendations for lifestyle modifications, and reduced energetic exercise significantly (p=0.002). Before study entry, and after 1 year, all underwent bicycle exercise tests with a ramp protocol. There were no differences in exercise capacity between the groups at entry, or follow-up, when median exercise capacity in the groups were virtually identical (2.4, 2.3, and 2.3 watt/kg and 55, 55, and 55 watt/(height in metre) 2 in control, selective, and non-selective groups, respectively. Maximum heart rate decreased in the selective (-29%, p=0.04) and non-selective (-24%, p=0.002) groups. No patient developed a pathological blood-pressure response to exercise because of β-blocker therapy. Boys were more frequently risk-factor positive than girls (75% versus 33%, p=0.048) and had higher physical activity scores than girls at study-entry (p=0.011).

CONCLUSIONS

Neither selective nor non-selective β-blockade causes significant reductions in exercise capacity in patients with hypertrophic cardiomyopathy above that induced by lifestyle changes.

Shortening baroreflex delay in hypertrophic cardiomyopathy patients -- an unknown effect of β-blockers

AIMS

Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy and impaired diastolic and systolic function. Abnormal sympathetic-parasympathetic balance is a potential stimulus for left ventricular hypertrophy in HCM patients. β-Blockers are routinely used in HCM for their strong negative inotropic effect; however, these drugs also influence the sympathetic-parasympathetic balance. This study aimed to determine the autonomic control of the cardiovascular system and the autonomic effects of β-blockers in HCM patients treated or untreated with β-blockers.

METHODS

Among 51 HCM outpatients (18-70 years old; 29 men) there were 19 individuals with no medication and 32 subjects treated with a β-blocker. Fourteen age- and gender-matched (23-70 years old; nine men) healthy volunteers were enrolled in the control group. Continuous, non-invasive finger blood pressure was recorded during supine rest for 30 min. Autonomic regulation of the cardiovascular system was measured by heart rate variability and spontaneous baroreflex function (cross-correlation sequence method).

RESULTS

The mean pulse interval, time domain and spectral measures of heart rate variability and baroreflex sensitivity were comparable between HCM patients, treated or not with β-blockers, and the control group. However, the delay of the baroreflex was significantly longer in HCM patients who were not treated with β-blockers [2.0 (1.6-2.3) s] in comparison with HCM patients receiving β-blockers [1.4 (1.1-1.8) s; P = 0.0072] or control subjects [1.2 (0.8-1.8) s; P = 0.0025]. This delay did not differ between HCM patients treated with β-blockers and the control group.

CONCLUSIONS

Hypertrophic cardiomyopathy not treated with β-blockers is accompanied by prolonged baroreflex delay. The use of β-blockers normalizes this delay.

Insights and challenges in hypertrophic cardiomyopathy, 2012

We present a contemporary overview of hypertrophic cardiomyopathy (HCM), incorporating recent thinking on disease mechanisms and advances in therapy. Clinical, pathological, genetic, and mechanistic definitions of HCM are discussed. The genetic profile of HCM in both adults and children is explored to the extent of present knowledge. The spectrum of morphological and histological abnormalities in HCM is reviewed, including involvement of the right ventricle, which is less widely recognised. Morbidity and mortality from HCM may result from diastolic dysfunction, ischaemia, left ventricular outflow tract obstruction, mitral regurgitation, supraventricular and ventricular arrhythmia, or--less commonly--progression to "burnt out" disease or sudden cardiac death (SCD). Defibrillators offer an efficacious means of averting SCD, but are not without their complications, underscoring the importance of identifying at-risk cases. We address the strengths and weaknesses of prognostication based on readily obtainable clinical markers, and discuss the integration of auxiliary approaches such as genotyping, cardiovascular magnetic resonance, and fractionation analysis into existing risk stratification guidelines. Finally, we provide an update on the pharmacological and interventional management of HCM, including the advent of disease-modifying therapy.

Relation of pulse pressure to blood pressure response to exercise in patients with hypertrophic cardiomyopathy

Almost one third of patients with hypertrophic cardiomyopathy (HC) will have an abnormal blood pressure response (ABPR) to exercise, and this has been associated with a greater risk of sudden cardiac death. In the present study, we examined the association between the steady (mean arterial pressure) and pulsatile (pulse pressure) blood pressure components as they relate to ABPR in patients with HC (n = 70). All patients completed a standard Bruce protocol during symptom-limited stress testing with concurrent hemodynamic measurements. Pulse pressure (PP) was significantly greater in patients with HC with an ABPR (n = 19) than in the patients with HC without an ABPR to exercise (p <0.05). According to binary logistic regression analysis, PP at rest was a significant predictor of ABPR in patients with HC (p <0.05). Mean arterial pressure was not significantly different between the 2 groups, nor was it a predictor of an ABPR in the presence of HC. Those within the greatest tertile of PP at rest were 4.8 times more likely to have an ABPR than those within the lowest PP tertile (95% confidence interval 1.24 to 18.2, p <0.05). In conclusion, elevations in PP at rest might identify patients with HC at a greater risk of having an ABPR during exercise.

Hypertrophic cardiomyopathy in childhood and adolescence - strategies to prevent sudden death

Clinically overt hypertrophic cardiomyopathy is the most common cause of sudden unexpected death in childhood and has significantly higher sudden death mortality in the 8- to 16-year age range than in the 17- to 30-year age range. A combination of electrocardiographic risk factors (a limb-lead ECG voltage sum >10 mV) and/or a septal wall thickness >190% of upper limit of normal for age (z-score > 3.72) defines a paediatric high-risk patient with great sensitivity. Syncope, blunted blood pressure response to exercise, non-sustained ventricular tachycardia and a malignant family history are additional risk factors. Of the medical treatments used, only beta-blocker therapy with lipophilic beta-blockers (i.e. propranolol, metoprolol or bisoprolol) have been shown to significantly reduce risk of sudden death, with doses ≥ 6 mg/kg BW in propranolol equivalents giving around a tenfold reduction in risk. Disopyramide therapy is a very useful adjunct to beta-blockers to improve prognosis in those patients that have dynamic outflow obstruction in spite of large doses of beta-blocker, and its use in patients with hypertrophic cardiomyopathy is not associated with significant pro-arrhythmia mortality. Calcium-channel blockers increase the risk of heart failure-associated death in hypertrophic cardiomyopathy (HCM) patients with severe generalized hypertrophy and should be avoided in such patients. Amiodarone does not protect against sudden death, and long-term use in children usually has to be terminated because of side effects. Therapy with internal cardioverter defibrillator implantation has high paediatric morbidity, 27% incidence of inappropriate shocks, and does not absolutely protect against mortality but is indicated as secondary prevention or in very high-risk patients.