Mechanisms of exercise limitation in hypertrophic cardiomyopathy

Association of Impaired Left Ventricular Mitral Filling from 4D Flow Cardiac MRI and Prognosis of Hypertrophic Cardiomyopathy

Purpose To investigate whether the peak early filling rate normalized to the filling volume (PEFR/FV) estimated from four-dimensional (4D) flow cardiac MRI may be used to assess impaired left ventricular (LV) filling and predict clinical outcomes in individuals with hypertrophic cardiomyopathy (HCM). Materials and Methods Cardiac MRI with a 4D flow sequence and late gadolinium enhancement (LGE), as well as echocardiography, was performed in 88 individuals: 44 participants with HCM from a French prospective registry (ClinicalTrials.gov; NCT01091480) and 44 healthy volunteers matched for age and sex. In participants with HCM, a composite primary end point was assessed at follow-up, including unexplained syncope, new-onset atrial fibrillation, hospitalization for congestive heart failure, ischemic stroke, sustained ventricular arrhythmia, septal reduction therapy, and cardiac death. A Cox proportional hazard model was used to analyze associations with the primary end point. Results PEFR/FV was significantly lower in the HCM group (mean age, 51.8 years ± 18.5 [SD]; 29 male participants) compared with healthy volunteers (mean, 3.35 sec-1 ± 0.99 [0.90-5.20] vs 4.42 sec-1 ± 1.68 [2.74-11.86]; P < .001) and correlated with both B-type natriuretic peptide (BNP) level (r = -0.31; P < .001) and the ratio of pulsed Doppler early transmitral inflow to Doppler tissue imaging annulus velocities (E/E'; r = -0.54; P < .001). At a median follow-up of 2.3 years (IQR, 1.7-3.3 years), the primary end point occurred in 14 (32%) participants. A PEFR/FV of 2.61 sec-1 or less was significantly associated with occurrence of the primary end point (hazard ratio, 9.46 [95% CI: 2.61, 45.17; P < .001] to 15.21 [95% CI: 3.51, 80.22; P < .001]), independently of age, BNP level, E/E', LGE extent, and LV and left atrial strain according to successive bivariate models. Conclusion In HCM, LV filling evaluated with 4D flow cardiac MRI correlated with Doppler and biologic indexes of diastolic dysfunction and predicted clinical outcomes. Keywords: Diastolic Function, Left Ventricular Filling, Hypertrophic Cardiomyopathy, Cardiac MRI, 4D Flow Sequence Clinical trial registration no. NCT01091480 Supplemental material is available for this article. © RSNA, 2024.

Cardiopulmonary Exercise Test in Patients with Hypertrophic Cardiomyopathy: A Systematic Review and Meta-Analysis

BACKGROUND

Patients with chronic diseases frequently adapt their lifestyles to their functional limitations. Functional capacity in Hypertrophic Cardiomyopathy (HCM) can be assessed by stress testing. We aim to review and analyze the available data from the literature on the value of Cardiopulmonary Exercise Test (CPET) in HCM. Objective measurements from CPET are used for evaluation of patient response to traditional and new developing therapeutic measurements.

METHODS

A systematic review of the literature was conducted in PubMed, Web of Science and Cochrane in Mar-20. The original search yielded 2628 results. One hundred and two full texts were read after the first screening, of which, 69 were included for qualitative synthesis. Relevant variables to be included in the review were set and 17 were selected, including comorbidities, body mass index (BMI), cardiac-related symptoms, echocardiographic variables, medications and outcomes.

RESULTS

Study sample consisted of 69 research articles, including 11,672 patients (48 ± 14 years old, 65.9%/34.1% men/women). Treadmill was the most common instrument employed (n = 37 studies), followed by upright cycle-ergometer (n = 16 studies). Mean maximal oxygen consumption (VO2max) was 22.3 ± 3.8 mL·kg^-1·min^-1. The highest average values were observed in supine and upright cycle-ergometer (25.3 ± 6.5 and 24.8 ± 9.1 mL·kg^-1·min^-1; respectively). Oxygen consumption in the anaerobic threshold (ATVO2) was reported in 18 publications. Left ventricular outflow tract gradient (LVOT) > 30 mmHg was present at baseline in 31.4% of cases. It increased to 49% during exercise. Proportion of abnormal blood pressure response (ABPRE) was higher in severe (>20 mm) vs. mild hypertrophy groups (17.9% vs. 13.6%, p < 0.001). Mean VO2max was not significantly different between severe vs. milder hypertrophy, or for obstructive vs. non-obstructive groups. Occurrence of arrhythmias during functional assessment was higher among younger adults (5.42% vs. 1.69% in older adults, p < 0.001). Twenty-three publications (9145 patients) evaluated the prognostic value of exercise capacity. There were 8.5% total deaths, 6.7% cardiovascular deaths, 3.0% sudden cardiac deaths (SCD), 1.2% heart failure death, 0.6% resuscitated cardiac arrests, 1.1% transplants, 2.6% implantable cardioverter defibrillator (ICD) therapies and 1.2 strokes (mean follow-up: 3.81 ± 2.77 years). VO2max, ATVO2, METs, % of age-gender predicted VO2max, % of age-gender predicted METs, ABPRE and ventricular arrhythmias were significantly associated with major outcomes individually. Mean VO2max was reduced in patients who reached the combined cardiovascular death outcome compared to those who survived (-6.20 mL·kg^-1·min^-1; CI 95%: -7.95, -4.46; p < 0.01).

CONCLUSIONS

CPET is a valuable tool and can safely perform for assessment of physical functional capacity in patients with HCM. VO2max is the most common performance measurement evaluated in functional studies, showing higher values in those based on cycle-ergometer compared to treadmill. Subgroup analysis shows that exercise intolerance seems to be more related to age, medication and comorbidities than HCM phenotype itself. Lower VO2max is consistently seen in HCM patients at major cardiovascular risk.

Respiratory dyssynchrony is a predictor of prognosis in patients with hypertrophic non-obstructive cardiomyopathy

BACKGROUND

Respiratory dyssynchrony (RD) is a phenomenon that may be reflected by reduced breathing efficiency (CO₂ output relative to minute ventilation, V̇E/V̇CO₂ slope) or by Exercise oscillatory ventilation (EOV). Low breathing efficiency and EOV indicate a worse prognosis in chronic heart failure patients with reduced ejection fraction (HFrEF). However, only little is known about their role in other forms of structural myocardial diseases. In this study, we assessed the prognostic impact of RD in hypertrophic non-obstructive cardiomyopathy (HNCM) as a subgroup of patients with heart failure and preserved ejection fraction (HFpEF).

METHODS AND RESULTS

We selected n = 132 HNCM patients (pts) who underwent cardiopulmonary exercise testing (CPET) during baseline assessment. The average follow-up was 4.3 ± 3.6 years. The primary endpoint was a composite of death, heart transplantation (HTX), and implantation of a ventricular assist device (VAD). Respiratory dyssynchrony, as measured by EOV, was recorded in 18 pts. (14%), and as measured by a V̇E/V̇CO₂ relationship of higher than 34 in 34 pts. (26%). In total, 22 (16.7%) pts. met the endpoint. Multivariate COX regression Analysis were made for EOV, V̇E/V̇CO₂ and the combination of EOV andV̇E/V̇CO₂. All parameters correlated significantly with the endpoint: EOV (hazard ratio [HR]: 3.7; p = 0.006), V̇E/V̇CO₂ > 34 (HR: 5.6; p = 0.001) and EOV andV̇E/V̇CO₂: (HR: 6.1; p ≤ 0.001).

CONCLUSION

This is the first study to demonstrate the prognostic impact of RD on pts. with HNCM, and to investigate EOV as a novel factor to aid risk stratification in HNCM.

Left ventricular end-diastolic volume predicts exercise capacity in patients with a normal ejection fraction

BACKGROUND

Exercise capacity is a powerful predictor of all-cause mortality. The duration of exercise with treadmill stress testing is an important prognostic marker in both healthy subjects and patients with cardiovascular disease. Left ventricular (LV) structure is known to adapt to sustained changes in level of physical activity.

HYPOTHESIS

Poor exercise capacity in patients with a preserved LV ejection fraction (LVEF) should be reflected in smaller LV dimensions, and a normal exercise capacity should be associated with larger LV dimensions, irrespective of comorbidities.

METHODS

This hypothesis was first tested in a cross-sectional analysis of 201 patients with normal chamber dimensions and preserved LVEF who underwent a clinically indicated treadmill stress echocardiogram using the Bruce protocol (derivation cohort). The best LV dimensional predictor of exercise capacity was then tested in 1285 patients who had a Bruce-protocol treadmill exercise stress test and a separate transthoracic echocardiogram (validation cohort).

RESULTS

In the derivation cohort, there was a strong positive relationship between exercise duration and LV end-diastolic volume deciles (r ²  = 0.85; P < 0.001). Regression analyses of several LV dimensional parameters revealed that the body surface area-based LV end-diastolic volume index was best suited to predict exercise capacity (P < 0.0001). In a large validation cohort, LV end-diastolic volume was confirmed to predict exercise capacity (P < 0.0001).

CONCLUSIONS

Among patients referred for outpatient stress echocardiography who have a preserved LVEF and no evidence of myocardial ischemia, we found a strong positive association between LV volume and exercise capacity.

Clinical Profile of Athletes With Hypertrophic Cardiomyopathy

BACKGROUND

The phenotype of individuals with hypertrophic cardiomyopathy (HCM) who exercise regularly is unknown. This study characterized the clinical profile of young athletes with HCM.

METHODS AND RESULTS

The electrical, structural, and functional cardiac parameters from 106 young (14-35 years) athletes with HCM were compared with 101 sedentary HCM patients. A subset of athletes with HCM exhibiting morphologically mild (13-16 mm), concentric disease was compared with 55 healthy athletes with mild physiological left ventricular hypertrophy (LVH). Most athletes with HCM (96%) exhibited T-wave inversion and had milder LVH (15.8±3.4 mm versus 19.7±6.5 mm, P<0.001), larger left ventricular cavity dimensions (47.8±6.0 mm versus 44.3±7.7 mm, P<0.001), and superior indices of diastolic function (average E/E' 7.9±2.4 versus 10.7±3.9, P<0.001) compared with sedentary HCM patients. In athletes with HCM, LVH was frequently (36%) confined to the apex and only 15 individuals (14%) exhibited mild concentric LVH mimicking physiological LVH. In these 15 athletes, conventional structural and functional cardiac parameters showed modest sensitivity and specificity for differentiating HCM from physiological LVH: 13% had a left ventricular cavity >54 mm, 87% had a left atrium ≤40, and 100% had an E/E' <12.

CONCLUSIONS

Athletes with HCM exhibit less LVH, larger left ventricular cavities, and normal indices of diastolic function compared with sedentary patients. Only a minority of athletes with HCM constitute the conventional gray zone of mild, concentric LVH. In this minority, conventional echocardiographic parameters alone are insufficient to differentiate HCM from physiological LVH and should be complemented by additional structural and functional assessments to minimize the risk of false reassurance.

Early diastolic function during exertion influences exercise intolerance in patients with hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) patients with preserved left ventricular ejection fraction (LVEF) often develop dyspnea and exercise intolerance. Diastolic dysfunction may contribute to exercise intolerance in these patients. This study aimed to clarify our hypothesis as to whether diastolic function rather than systolic function would be associated with exercise intolerance in HCM using two-dimensional (2D) speckle tracking echocardiography during exercise.

METHODS

Thirty-three HCM patients (mean age 59.3 ± 15.7 years) underwent 2D speckle tracking echocardiography at rest and during submaximal semi-supine bicycle exercise. Global longitudinal strain (LS), LS rate during systole (LSRs), early diastole (LSRe), and late diastole (LSRa) were measured. The symptom-limited cardiopulmonary exercise testing was performed using a cycle ergometer for measuring the peak oxygen consumption (peak [Formula: see text]).

RESULTS

In the multivariate linear regression analysis, peak [Formula: see text] did not associate with strain or strain rate at rest. However, peak [Formula: see text] correlated with LS (β = -0.403, p = 0.007), LSRe (β = 6.041, p = 0.001), and LSRa (β = 5.117, p = 0.021) during exercise after adjustment for age, gender, and heart rate. The first quartile peak [Formula: see text] (14.2 mL/min/kg) was assessed to predict exercise intolerance. The C-statistic of delta LSRe was 0.74, which was relatively greater than that of delta LS (0.70) and delta LSRa (0.58), indicating that early diastolic function rather than systolic and late diastolic function affects exercise intolerance.

CONCLUSIONS

LSRe during exercise is closely associated with the peak [Formula: see text]. Early diastolic function during exercise is an important determinant of exercise capacity in patients with HCM.

Relationship between baseline resting diastolic function and exercise capacity in patients with hypertrophic cardiomyopathy undergoing treadmill stress echocardiography: a cohort study

OBJECTIVE

Diastolic dysfunction (DD) is often incriminated in the symptomatology of patients with hypertrophic cardiomyopathy (HCM), but with limited supporting data. This study sought to assess the relationship between baseline diastolic function and exercise capacity in patients with HCM.

DESIGN

Retrospective study.

SETTING

Tertiary referral centre from Cleveland, Ohio, USA.

PARTICIPANTS

695 consecutive patients with a diagnosis of HCM who underwent exercise stress echocardiography between 1996 and 2011.

PRIMARY AND SECONDARY OUTCOME MEASURES

Diastolic function was reassessed from the resting echocardiograms by two blinded board-certified cardiologists. Maximal metabolic equivalents (MET) were extracted from the records. Multivariate regression analysis was performed to determine independent predictors of METs achieved.

RESULTS

Of 695 patients, 130 were excluded because of inability to assess diastolic function. There was no significant difference in maximal METs achieved between those excluded and included in the analysis (p=0.80). There were 495 remaining patients with a mean age (SD) of 50 (15) years, and 32% women among whom 102 (21%) had normal diastolic function, 243 (49%) stage 1 DD; 131 (26%) stage 2 DD and 19 (4%) stage 3 DD. Patients with advanced DD had lower maximal METs achieved compared with those with normal diastolic function (OR 3.18(1.96 to 5.14) for stage 1 versus normal, and 3.21(1.89 to 5.43) for stage ≥2 versus normal, p<0.0001 for both). After adjustment for demographics, comorbidities, echocardiographic parameters and haemodynamics, baseline DD was not an independent predictor of maximal METs achieved.

CONCLUSIONS

Although baseline DD is common in patients with HCM, it does not predict maximal METs achieved beyond traditional risk factors.

Effects of exercise on the duration of diastole and on interventricular phase differences in patients with hypertrophic cardiomyopathy: relationship to cardiac output reserve

BACKGROUND

Our study sought to characterize the effect of exercise on the duration of left ventricular (LV) diastole and interventricular dyssynchrony in patients with hypertrophic cardiomyopathy (HCM). We hypothesized that an abnormally shortened diastolic time may adversely affect cardiac performance.

METHODS

We studied 49 symptomatic patients with HCM during incremental exercise. Twenty-nine patients had obstructive disease (HOCM) and 20 no resting or provocable gradient (HNCM). Right heart catheterization and high temporal resolution radionuclide angiography were simultaneously performed. The loss of diastolic time per beat (LDT(RR)) was quantified using a regression equation obtained from a healthy control group (n = 30).

RESULTS

During rest and peak exercise, a significant shortening of the relative duration of LV diastole (35.6 +/- 5 vs. 38.0 +/- 3 s/min and 29.3 +/- 6 vs. 32.4 +/- 3 s/min; P < or = .02) and an increased interventricular phase delay were evident in patients with HOCM compared to controls. Baseline and peak exercise LDT(RR) values were inversely related to cardiac output reserve and exercise duration. In multivariate analysis, LDT(RR) at peak exercise was identified as an independent predictor of cardiac output reserve.

CONCLUSIONS

In HOCM, baseline abnormalities of the relative duration of LV systolic and diastolic time aggravate during exercise. The disproportionate shortening of diastolic time may significantly impair cardiac efficiency by restricting diastolic filling.

Echocardiographic predictors of severe heart failure symptoms in hypertrophic cardiomyopathy patients with sinus rhythm

Background

Symptoms in hypertrophic cardiomyopathy (HC) appear to be caused by diastolic dysfunction, myocardial ischemia, left ventricle (LV) outflow obstruction, and atrial fibrillation. However, clinical deterioration and severe heart failure symptoms can be observed in patients without any of these factors. Thus, the aim of this study is to determine the echocardiographic predictors of severe heart failure symptoms in patients with HC.

Methods and results

86 HC patients were compared according to symptomatic status. Patients with severe heart failure symptoms were older, preponderantly female, had more often LV outflow obstruction and mitral regurgitation, longer E wave deceleration time (EDt), higher E/Ea ratios and lower LV tissue Doppler (TD) velocities when compared to rest of the patients. LV outflow obstruction (r = 0.43, R² = 0.19, p < 0.0001), LV lateral mitral annular systolic TD velocity (LMSa) (r = 0.51, R² = 0.26, p < 0.006) and EDt (r = 0.55, R² = 0.30, p < 0.027) were found to be the independent predictors for severe heart failure symptoms in forward stepwise regression.

Conclusion

In HCM patients with sinus rhythm and normal LV systolic function, LMSa, EDt and LV outflow obstruction are independent predictors of heart failure symptoms. Diastolic dysfunction determined with EDt, occult systolic dysfunction which is detected with TD analysis, and afterload increase as result of LV outflow obstruction seem to be the main echocardiographic factors affecting symptomatic status in HCM patients with sinus rhythm and normal systolic function.

Prevalence, clinical significance, and genetic basis of hypertrophic cardiomyopathy with restrictive phenotype

OBJECTIVES

The purpose of this study was to determine the prevalence, clinical significance, and genetic basis of hypertrophic cardiomyopathy (HCM) with "restrictive phenotype" characterized by restrictive filling and minimal or no left ventricular hypertrophy.

BACKGROUND

Hypertrophic cardiomyopathy is a heterogeneous myocardial disorder with a broad spectrum of clinical presentation and morphologic features. Recent reports indicated that some patients with restrictive cardiomyopathy, which is an uncommon condition defined by restrictive filling and reduced diastolic volumes with normal or near normal left ventricular wall thickness and contractile function, have features suggestive of HCM with mutations in cardiac troponin I, myocyte disarray at explant/autopsy, and relatives with HCM. Systematic evaluation of the restrictive phenotype in HCM patients has not been performed.

METHODS

We evaluated 1,226 patients from 688 consecutive HCM families to identify individuals who fulfilled diagnostic criteria for "restrictive phenotype."

RESULTS

Nineteen of 1,226 affected individuals (1.5%) from 16 families (2.3%) had the "restrictive phenotype." During follow up (53.7 +/- 49.2 months), 17 patients (89%) experienced dyspnea (New York Heart Association functional class > or =2). The 5-year survival rate from all-cause mortality, cardiac transplantation, or implantable cardioverter-defibrillator discharge was 56.4%. Mutation analysis for 5 sarcomere genes was feasible in 15 of 16 probands. Mutations were found in 8: 4 in beta-myosin heavy chain, and 4 in cardiac troponin I.

CONCLUSIONS

The "restrictive phenotype" in isolation is an uncommon presentation of the clinical spectrum of HCM and is associated with severe limitation and poor prognosis. This phenotype may be associated with beta-myosin heavy chain and cardiac troponin I mutations.

Tissue Doppler-Derived Indices Predict Exercise Capacity in Patients With Apical Hypertrophic Cardiomyopathy

BACKGROUND

Although impaired left ventricular (LV) diastolic function is a prominent feature of hypertrophic cardiomyopathy (HCM), diastolic function and its relation to exercise capacity in apical HCM (ApHCM) has not been explored previously. This study was sought to determine the relationship between diastolic mitral annular velocities combined with conventional Doppler indexes and exercise capacity in patients with ApHCM.

PATIENTS

Twenty-nine patients with ApHCM (24 men; mean age +/- SD, 57 +/- 10 years) underwent supine bicycle exercise with simultaneous respiratory gas analysis and two-dimensional and Doppler echocardiographic study.

RESULTS

The mitral inflow velocities (early filling [E], late filling, and deceleration time) were traced and measured. Early diastolic mitral annular velocity (E') was measured at the septal corner of mitral annulus by Doppler tissue imaging (DTI) from the apical four-chamber view. Pro-brain natriuretic peptide (proBNP) was measured at the time of echocardiography using a quantitative electrochemiluminescence immunoassay. E/E' ratio correlated inversely with maximal oxygen uptake (Vo(2)max) [r = - 0.47, p = 0.0106]. There was a significant positive correlation between E' and Vo(2)max (r = 0.41, p = 0.024). However, no correlation was found between conventional two-dimensional, Doppler indices, and proBNP and Vo(2)max). Of all the echocardiographic and clinical parameters assessed, E/E' ratio had the best correlation with exercise capacity (r - 0.47) and was the strongest independent predictor of Vo(2)max by multivariate analysis (p = 0.0106).

CONCLUSIONS

DTI-derived indexes (E', E/E' ratio), an estimate of myocardial relaxation and LV filling pressures, correlate with exercise capacity in patients with ApHCM, suggesting that abnormal diastolic function may be a factor limiting exercise capacity.

Significance and relation between magnitude of left ventricular hypertrophy and heart failure symptoms in hypertrophic cardiomyopathy

In hypertrophic cardiomyopathy (HC), an important subgroup of patients develop progressive and disabling symptoms that are related to heart failure and death. Although a direct relation has been demonstrated between left ventricular (LV) wall thickness and likelihood of sudden and unexpected death (usually in patients who are asymptomatic or mildly symptomatic), it is unresolved whether magnitude of hypertrophy is similarly associated with severity of heart failure. To determine the relation of LV wall thickness to heart failure symptoms in HC, 700 consecutive patients who had HC were assessed by 2-dimensional echocardiography. The relation between maximum level of heart failure symptoms by New York Heart Association functional class and maximum LV wall thickness was not linear but rather parabolic. Therefore, marked symptoms were most commonly associated with moderate degrees of LV hypertrophy (wall thickness 16 to 24 mm; 27%) but less frequently with extreme hypertrophy (>/=30 mm 13%) or mild hypertrophy (</=15 mm; 19%, p = 0.0001). Mean New York Heart Association functional class showed a similar pattern with respect to moderate hypertrophy (1.9 +/- 0.8), mild hypertrophy (1.6 +/- 0.9), and extreme hypertrophy (1.6 +/- 0.7, p = 0.005). Multivariable regression analysis showed the parabolic relation between heart failure symptoms and magnitude of LV hypertrophy to be independent of other hypertrophic cardiomyopathy related clinical variables. In conclusion, no direct relation was evident between symptoms of heart failure and magnitude of LV wall thickness, with implications for the natural history of HC.

Elevated serum markers for collagen synthesis in patients with hypertrophic cardiomyopathy and diastolic dysfunction

OBJECTIVES

The hypothesis of impaired collagenolysis in patients with hypertrophic cardiomyopathy (HCM) was tested by measuring serum markers of type-I collagen metabolism. These markers were correlated with echocardiographic parameters of diastolic function.

BACKGROUND

HCM is a common disease in the adult population with a wide range of clinical manifestations. Left ventricular hypertrophy and increased intramyocardial collagen content are known to cause diastolic dysfunction in patients with HCM.

METHODS

In 26 patients with HCM and 38 control subjects (aged: 57+/-3 and 54+/-2 years, p=n.s.) serum levels of collagenolytic matrixmetalloproteinase-1 (MMP-1) and its inhibitor TIMP-1, the markers for collagen type-I synthesis (PICP) and degradation (ICTP) were determined by ELISA and RIA. Diastolic function were determined by Doppler echocardiography.

RESULTS

Free TIMP-1 was elevated in HCM compared to controls (216,78+/-9,89 vs 183.77+/-7.57 ng/ml ; p=0.006) as well as PICP (165.92+/-10.26 vs 114.57+/-6.38 mug/l; p<0.001). Free MMP-1 was significantly lower in HCM (1.13+/-0.20 vs 2.33+/-0.34; p=0.01). ICTP did not differ. The MMP-1/TIMP-1 ratio was significantly lower in HCM (0.006+/-0.001 vs 0.012+/-0.001, p=0.003). PICP correlated positively with diastolic E/A ratio (r=0.389; p=0.05) and septal thickness (r=0.484; p=0.01).

CONCLUSIONS

Serum marker of collagen synthesis (PICP) is increased in patients with HCM. Increased marker for inhibition of collagenolysis (TIMP-1) and a disturbed balance of collagen synthesis and degradation (ratio) with a predominance of inhibition of collagenolysis indicates collagen accumulation (fibrosis), which explains passive diastolic dysfunction in patients with HCM.

Left atrial volumetric remodeling is predictive of functional capacity in nonobstructive hypertrophic cardiomyopathy

BACKGROUND

The left atrium is afterload sensitive, responding to immediate changes in left ventricular (LV) diastolic pressure, and left atrial volumetric remodeling has been reported in conditions associated with abnormal diastolic function. We examined the relationship between left atrial volumetric remodeling and objective measures of exercise capacity in patients with nonobstructive hypertrophic cardiomyopathy (HCM).

METHODS

We compared LA volume indices, other 2-dimensional and Doppler echocardiographic parameters, invasive hemodynamic measures, and magnetic resonance imaging (MRI)-derived LV mass with exercise duration, maximal oxygen uptake (MV* O2), anaerobic threshold (AT), and ventilatory efficiency (VE/V* CO2 slope) in 43 patients with nonobstructive HCM. Patients underwent cardiac catheterization within 48 hours and metabolic stress testing within 1 week of their echocardiogram and MRI examinations.

RESULTS

Left atrial volume at end-ventricular systole (LA max) and end-atrial emptying (LA min) correlated with MV* O2 (r = -0.39, P < .01 for both), AT (r = -0.42, r = -0.39, respectively, P < .01 for both), and VE/V* CO2 slope (r = 0.45, P = .003; r = 0.41, P = .008). Patients with an LA max > or =33 mL/m2 had significantly lower MV* O2 (P = .025) and AT levels (P = .017) and higher VE/V* CO2 slope levels (P = .004) as compared with patients with a smaller LA size. In multivariate analysis, MRI-determined LV mass, which was not a univariate correlate of exercise tolerance, provided additional effect when combined with LA volume index.

CONCLUSIONS

Left atrial volumetric remodeling predicts exercise capacity in nonobstructive HCM and may reflect chronic LV diastolic burden. This simple noninvasive measure of LA size may provide a long-term indication of the effects of chronically elevated filling pressures in patients with HCM and further studies testing its prognostic value are necessary.

Left ventricular diastolic dysfunction and diastolic heart failure

Thirty to fifty percent of patients presenting with signs and symptoms of heart failure have a normal left ventricular (LV) systolic ejection fraction. The clinical examination cannot distinguish these patients (diastolic heart failure) from those with a depressed ejection fraction (systolic heart failure), but echocardiography can. The management of diastolic heart failure has two major objectives. The first is to reverse the consequences of diastolic dysfunction (e.g., venous congestion), and the second is to eliminate or reduce the factors responsible for diastolic dysfunction (e.g., myocardial hypertrophy, fibrosis, and ischemia).

[Functional assessment of patients with hypertrophic cardiomyopathy by maximal oxygen consumption]

INTRODUCTION AND OBJECTIVES

Differences between anatomical severity and clinical manifestations are frequent in patients with hypertrophic cardiomyopathy. Our objective was to assess functional capacity in a consecutive group of patients with hypertrophic cardiomyopathy measuring exercise aerobic parameters, as well as clinical and echocardiographic variables.

PATIENTS AND METHOD

We studied 98 consecutive patients with hypertrophic cardiomyopathy. All patients underwent both echocardiographic and cardiopulmonary exercise testing. The control group consisted of 22 untrained persons. We studied exercise capacity by analyzing maximal oxygen consumption and aerobic functional capacity, among other variables.

RESULTS

Patients with hypertrophic cardiomyopathy attained significantly lower maximal oxygen consumption values than controls (24.1 5.9 vs 36.4 5.9 ml/kg/min; p = 0.0001). Maximal aerobic capacity was significantly different among patients with NYHA functional capacity class I, II or III (78.9 13.5%; 71.9 14.7%; 63.9 15.7%; p = 0.009). However, considerable overlap was found between groups in maximal aerobic capacity. Functional impairment was greater in patients with left ventricular thickness > 20 mm, ejection fraction < 50%, left atrial dimension > 45 mm and pseudonormal or restrictive transmitral flow pattern.

CONCLUSIONS

Patients with hypertrophic cardiomyopathy show significant functional impairment, which is difficult to detect from their clinical manifestations. Optimal assessment requires cardiopulmonary exercise testing.

Remodelado ventricular izquierdo tras ablación septal percutánea con alcohol en pacientes con miocardiopatía hipertrófica obstructiva: estudio ecocardiográfico

INTRODUCTION

In patients with hypertrophic obstructive cardiomyopathy, obstruction in the left ventricular outflow tract may generate more hypertrophy. Our aim was to evaluate the impact of reducing ventricular outflow tract obstruction on left ventricular hypertrophy and remodeling after alcohol septal ablation.

PATIENTS AND METHOD

20 patients with hypertrophic obstructive cardiomyopathy who underwent alcohol septal ablation were included. Doppler echocardiography was performed in all patients at baseline, immediately after alcohol septal ablation, and at 3 and 12 months' follow-up. Left ventricular diameters and wall thickness and pressure gradients in the ventricular outflow tract were determined.

RESULTS

Immediately after alcohol septal ablation, ventricular outflow tract pressure gradient decreased from 63.0 27.7 to 28.2 24.7 mmHg (p < 0.001), without significant changes in left ventricular dimensions. However, after 12 months we observed an increase in left ventricular end-diastolic (from 47.1 4.9 to 50.8 4.5 mm) and end-systolic diameter (from 27.1 3.0 to 33.7 4.6 mm), as well as a reduction in septal (from 19.5 4.0 to 15.5 2.7 mm) and posterior wall thickness (from 14.0 2.2 to 12.9 1.3 mm) (p < 0.01 in all cases). Left ventricular end-diastolic and end-systolic volumes increased (from 106.4 26.9 to 123.1 28.7 ml and from 50.2 17.3 to 56.7 18.3 ml, respectively, p < 0.01 in both cases), without changes in left ventricular ejection fraction. The reduction in ventricular outflow tract pressure gradient at 12 months' follow-up correlated significantly with the increase in left ventricular end-systolic diameter (r = 0.63; p < 0.01).

CONCLUSIONS

In patients with hypertrophic obstructive cardiomyopathy who underwent alcohol septal ablation, relief of ventricular outflow tract obstruction is associated with an increase in left ventricular chamber diameters and volume. These findings suggest that middle- and long-term ventricular remodeling and regression of hypertrophy occur in these patients, which may contribute to their clinical improvement.

Left atrial function preserves pulmonary circulatory pressure during pacing-tachycardia and contributes to exercise capacity in patients with idiopathic dilated cardiomyopathy in sinus rhythm, whose exercise is limited by dyspnea

The aim of this study was to determine whether left atrial (LA) function contributes to pulmonary circulatory pressure during pacing-tachycardia and exercise capacity in patients with idiopathic dilated cardiomyopathy (DCM). Thirty-two patients with DCM and in sinus rhythm had limited exercise capacity because of dyspnea. The correlation between peak oxygen consumption (VO2) and the variables of cardiac function by cardiac catheterization and 2-dimensional, Doppler echocardiography, and plasma neurohumoral factor levels was tested, as was the correlation between non-invasive LA functional parameters and pulmonary circulatory pressure during pacing-tachycardia. A significant correlation was observed between VO2 and LA dimension (r = -0.45, p < 0.01), the peak velocities of LA appendage empty flow during atrial systole (r = 0.63, p < 0.0001) and the pulmonary venous forward flow in early ventricular systole (PVS1; r = 0.74, p < 0.0001), as well as plasma brain natriuretic peptide (BNP) concentrations. The predictable equation to VO2 with the multiple regression analysis was: VO2 = -0.01 BNP+0.21 PVS1+15.4 (r = 0.81, p < 0.0001). Furthermore, LA functional variables derived from pulmonary venous flow, especially PVS1, but not plasma BNP concentration, were useful for predicting the degree of the increase in pulmonary circulatory pressure during pacing-tachycardia. Therefore, it is suggested that LA function contributes to exercise capacity through its influence on pulmonary hemodynamic reserve in patients with DCM with sinus rhythm whose exercise is limited by dyspnea.

Dynamic left ventricular outflow obstruction during lumbar laminectomy as an unexpected cause of intraoperative hypotension

We present a case of previously undiagnosed hypertrophic obstructive cardiomyopathy (HOCM) with left ventricular outflow obstruction in a woman anesthetized for lumbar hemilaminectomy and diskectomy. The treatment of her sudden unexplained hypotension was initially confounded by a diagnosis of compensated congestive heart failure and diuretic therapy. Swift intervention with transesophageal echocardiography revealed the tru pathology altering her intraoperative treatment and her subsequent chronic treatment for her heart condition.

Left ventricular diastolic function assessed using Doppler tissue imaging in patients with hypertrophic cardiomyopathy: relation to symptoms and exercise capacity

BACKGROUND

Conventional Doppler indices of left ventricular diastolic function do not correlate with symptoms or exercise capacity in patients with hypertrophic cardiomyopathy, because of their dependence on loading conditions. Diastolic mitral annular velocity measured using Doppler tissue imaging has been reported to be a preload independent index of left ventricular diastolic function.

OBJECTIVE

To determine the relation between diastolic annular velocities combined with conventional Doppler indices and symptoms or exercise capacity in hypertrophic cardiomyopathy.

METHODS

85 patients with hypertrophic cardiomyopathy and 60 normal controls were studied. Diastolic mitral annular velocities, transmitral left ventricular filling, and pulmonary venous velocities were measured.

RESULTS

Early diastolic velocities at lateral and septal annulus were lower in patients with hypertrophic cardiomyopathy than in controls (lateral Ea: 10 (3) v 18 (4) cm/s, p < 0.0001; septal Ea: 7 (2) v 12 (3) cm/s, p < 0.0001). Unlike conventional Doppler indices alone, transmitral early left ventricular filling velocity (E) to lateral Ea ratio correlated inversely with peak oxygen consumption (r = -0.42, p < 0.0001). Patients in New York Heart Association (NYHA) class III had a higher transmitral E to lateral Ea ratio (12.0 (4.6)) than those in NYHA class II (7.6 (3.1), p < 0.005) or class I (6.6 (2.6), p < 0.0001).

CONCLUSIONS

Early diastolic mitral annular velocities are reduced in patients with hypertrophic cardiomyopathy. Unlike conventional Doppler indices alone, the transmitral E to lateral Ea ratio correlates with NYHA functional class and exercise capacity.

Systolic dysfunction and blood pressure responses to supine exercise in patients with hypertrophic cardiomyopathy

Left ventricular function and blood pressure responses were evaluated in 56 patients with non-obstructive hypertrophic cardiomyopathy (HCM) and 12 control subjects by using a radionuclide ventricular function monitor during supine ergometer exercise. Patients with HCM were divided into 2 groups: (i) group A had no decrease in ejection fraction (EF) during exercise; and (ii) group B had a decrease in EF during exercise. During exercise, the change in end-diastolic volume did not differ between the 3 groups. In contrast, the change in end-systolic volume differed between the 3 groups (p<0.0001). The change in systolic blood pressure (SBP) also differed significantly between the 3 groups. The change in SBP in group B was smaller than that in the control group and group A, and changes in the EF and changes in the SBP between rest and peak exercise showed a significant correlation (p<0.005). These results suggest that exercise-induced systolic dysfunction in patients with non-obstructive HCM may contribute to abnormal blood pressure response in those patients.

Value of exercise testing in assessing clinical state and prognosis in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic disease of the sarcomeric contractile proteins. A majority of patients with HCM are limited in terms of functional capacity, and a minority of these patients die suddenly. The main aims of management are symptom alleviation and prevention of sudden cardiac death. In patients with HCM, cardiopulmonary exercise testing provides a much more accurate index of functional capacity than New York Heart Association classification status, and it is useful in assessing symptoms after various therapeutic strategies have been implemented. Exercise testing is also valuable in identifying patients with HCM who are at high risk of sudden cardiac death and is an integral part of the algorithm in risk stratification and delivery of prophylactic therapy. Also, cardiopulmonary exercise testing plays an important role in differentiating HCM from other conditions associated with left ventricular hypertrophy, such as physiologic athlete's heart. Therefore, during the last few years, cardiopulmonary exercise testing has provided insights into the diagnosis, determinants, and mechanisms of exercise limitation in HCM. This understanding aids physicians in targeting therapy and developing new treatment modalities.

The role of exercise testing in the evaluation of the patient with hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic disease of the sarcomeric contractile proteins that is characterized by left ventricular hypertrophy and myocyte disarray. The majority of patients are limited in terms of functional capacity and a minority die suddenly. The main aims of management are symptom alleviation and prevention of sudden cardiac death. In patients with HCM, cardiopulmonary exercise testing provides a more accurate index of functional capacity than New York Heart Association classification status and is useful in assessing symptoms following various therapeutic interventions. Cardiopulmonary exercise testing plays an important role in differentiating HCM from other conditions associated with left ventricular hypertrophy. Cardiopulmonary exercise testing is also valuable in identifying individuals at high risk of sudden cardiac death and is an integral part of the algorithm in risk stratification and delivery of prophylactic therapy. Over the past few years, cardiopulmonary exercise testing has provided insight into the determinants and mechanisms of exercise limitation. This understanding helps in targeting therapy and the development of new treatment modalities.

Diastolic Heart Failure

The diagnosis of diastolic heart failure (DHF) can be made when a patient has both symptoms and signs on physical exam of congestive heart failure (CHF), and normal left ventricular volume and ejection fraction. Documentation of abnormal diastolic function is confirmatory but not mandatory. Diastolic heart failure is a frequent cause of CHF (prevalence is 35% to 50%) and has a significant effect on mortality (5-year mortality rate is 25% to 35%) and morbidity (1-year readmission rate is 50%). Treatment should be targeted at symptoms, causal clinical disease, and underlying basic mechanisms. Symptom-targeted therapy: decrease pulmonary venous pressure using diuretics and long-acting nitrates, maintain atrial contraction and atrial ventricular synchrony, reduce heart rate using beta-adrenergic blockers and calcium channel blockers; increase exercise tolerance by reducing exercise- induced increases in blood pressure and heart rate using angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers, and calcium channel blockers. Disease-targeted therapy: prevent or treat myocardial ischemia, prevent or regress left ventricular hypertrophy. Mechanism-targeted therapy (future directions): modify neurohumoral activation using renin, angiotensin, and aldosterone system antagonists (ACE inhibitors, angiotensin II receptor blockade, aldosterone and renin antagonist); endothelin antagonists; nitric oxide agonists; and atrial natruretic peptide agonists; alter intracellular mechanisms; alter extracellular matrix structures.

Utility of metabolic exercise testing in distinguishing hypertrophic cardiomyopathy from physiologic left ventricular hypertrophy in athletes

OBJECTIVES

This study evaluated the role of metabolic (cardiopulmonary gas exchange) exercise testing in differentiating physiologic LVH in athletes from HCM.

BACKGROUND

Regular intensive training may cause mild increases in left ventricular wall thickness (LVWT). Although the degree of left ventricular hypertrophy (LVH) is typically less than that seen in hypertrophic cardiomyopathy (HCM), genetic studies have shown that a substantial minority of patients with HCM have an LVWT in the same range. The differentiation of physiologic and pathologic LVH in this "gray zone" can be problematic using echocardiography and electrocardiography alone.

METHODS

Eight athletic men with genetically proven HCM and mild LVH (13.9 +/- 1.1 mm) and eight elite male athletes matched for age, size and LVWT (13.4 +/- 0.9 mm) underwent symptom limited metabolic exercise stress testing. Peak oxygen consumption (pVO2), anaerobic threshold, oxygen pulse and respiratory exchange ratios were measured in both groups and compared with those observed in 12 elite and 12 recreational age- and size-matched athletes without LVH.

RESULTS

Elite athletes with LVH had significantly greater pVO2 (66.2 +/- 4.1 ml/kg/min vs. 34.3 +/- 4.1 ml/kg/min; p < 0.0001), anaerobic threshold (61.6 +/- 1.8% of the predicted maximum VO2 vs. 41.4 +/- 4.9% of the predicted maximum VO2; p < 0.001) and oxygen pulse (27.1 +/- 3.2 ml/beat vs. 14.3 +/- 1.8 ml/beat; p < 0.0001) than individuals with HCM. A pVO2 >50 ml/kg/min or >20% above the predicted maximum VO2 differentiated athlete's heart from HCM.

CONCLUSIONS

Metabolic exercise testing facilitates the differentiation between physiologic LVH and HCM in individuals in the "gray zone."

Utility of cardiopulmonary exercise in the assessment of clinical determinants of functional capacity in hypertrophic cardiomyopathy

The utility of metabolic gas exchange measurements in evaluating the severity and determinants of exercise limitation was studied during upright symptom-limited cardiopulmonary exercise in 135 consecutive patients with hypertrophic cardiomyopathy (HC) and 50 healthy age- and gender-matched volunteers. Peak oxygen consumption (VO(2)) was less than predicted (age, gender, and size) in 99% patients. Peak VO(2) was significantly associated with New York Heart Association functional class; however, there was considerable overlap of peak VO(2) between classes I and III (70 +/- 15%, 56 +/- 15%, 35 +/- 11%, respectively). Patients with abnormal blood pressure responses and patients with chronotropic incompetence during exercise had lower percent-predicted peak VO(2) than patients with normal blood pressure and heart rate responses during exercise (p = 0.0001 and p <0.001, respectively). Percent-predicted peak VO(2) was similar in patients with and without resting left ventricular outflow obstruction. Of those patients with resting gradients, however, there was a strong inverse correlation between the magnitude of the gradient and peak VO(2) (r = 0.5; p <0.001). In conclusion, peak VO(2) is significantly related to New York Heart Association functional class in this group of patients with HC, but peak VO(2) is a superior measure of cardiovascular performance in individual patients. Our peak VO(2) data indicate that mechanical obstruction has an adverse pathophysiologic effect on functional capacity and provide the rationale to support treatments aimed at gradient reduction. Low peak VO(2) characteristics including those with normal or near-normal left ventricular wall thickness suggests that measurement of peak VO(2) may aid in the differential diagnosis between HC and athlete's heart.

Exercise-induced ST-segment depression and systolic dysfunction in patients with nonobstructive hypertrophic cardiomyopathy

BACKGROUND

ST-segment depression is common in patients with hypertrophic cardiomyopathy (HCM). However, it is not clear whether exercise-induced ST-segment depression in patients with HCM and patent coronary arteries is associated with changes in left ventricular function.

METHODS

Left ventricular function was continuously evaluated in 53 patients with nonobstructive HCM during supine ergometer exercise with a radionuclide ventricular function monitor equipped with a cadmium telluride detector. On the basis of the ST-segment changes during exercise, the patients were divided into 2 groups: group N had no ST-segment depression, and group D had >/=0.1 mV ST-segment depression.

RESULTS

Exercise duration, blood pressure, heart rate, and rate-pressure product during exercise did not differ between the 2 groups. End-diastolic volume at rest and at peak exercise did not differ between groups D and N. In contrast, the end-systolic volume in group N decreased during exercise, whereas in group D it increased. As a result, the left ventricular ejection fraction in group D decreased from 70% +/- 7% to 59% +/- 15% (P <.0001), whereas ejection fraction in group N increased from 65% +/- 8% to 71% +/- 11% (P =.0002). There was a strong correlation between exercise-induced ST-segment depression and changes in ejection fraction from rest to peak exercise (P <.0001).

CONCLUSIONS

These results suggest that the exercise-induced ST-segment depression seen in patients with nonobstructive HCM is associated with systolic dysfunction during exercise.

Natural history of hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy is a disease of the cardiac sarcomere and is the most common inherited cardiovascular disorder affecting up to 1 in 500 people in the general population. The disease is typified by variable clinical penetrance and heterogeneous clinical expression, resulting in a wide range of clinical manifestations. Most patients have few if any symptoms and a relatively benign clinical course. A minority are at risk of serious complications including ventricular arrhythmia, sudden death, thromboembolism, congestive cardiac failure, heart block, and infective endocarditis. This article reviews the natural history of the disease, with particular emphasis on lessons learned from recent genetic studies.

Exercise gas exchange responses in the differentiation of pathologic and physiologic left ventricular hypertrophy

PURPOSE

The purpose of the present investigation was to examine differences that may exist in maximal and submaximal exercise gas exchange parameters and their use in differentiating pathological and physiological left ventricular hypertrophy.

METHODS

Exercise gas exchange responses were measured on-line during a maximal ramping cycle-ergometer exercise test in 10 young, male hypertrophic cardiomyopathy (HCM) patients, 11 elite triathletes, and 9 normal controls.

RESULTS

The HCM patients exhibited significantly lower VO2max, anaerobic threshold (AT) in both absolute terms (ATVO2) and as a percentage of VO2max (AT%VO2max), and oxygen-pulse (O2-pulse) compared with triathletes and normal controls. Elite triathletes exhibited significantly increased VO2max, %VO2max, ATVO2, AT%VO2max and O2-pulse compared with controls. The VE/VCO2 at AT was significantly increased in the HCM patients compared with triathletes and controls, whereas no difference was observed between triathletes and controls.

CONCLUSIONS

Maximal and submaximal exercise gas exchange responses may be used as an additional noninvasive tool in the differential diagnosis of physiologic and pathologic left ventricular hypertrophy.

Exercise capacity in hypertrophic cardiomyopathy depends on left ventricular diastolic function

Some studies have demonstrated that left ventricular (LV) diastolic function is the principal determinant of impaired exercise capacity in hypertrophic cardiomyopathy (HC). In this study we sought the capability of echocardiographic indexes of diastolic function in predicting exercise capacity in patients with HC. We studied 52 patients with HC while they were not on drugs;12 of them had LV tract obstruction at rest. Diastolic function was assessed by M-mode and Doppler echocardiography by measuring: (1) left atrial fractional shortening, and the slope of posterior aortic wall displacement during early atrial emptying on M-mode left atrial tracing; and (2) Doppler-derived transmitral and pulmonary venous flow velocity indexes. Exercise capacity was assessed by maximum oxygen consumption by cardiopulmonary test during cycloergometer upright exercise. Maximum oxygen consumption correlated with the left atrial fractional shortening (r = 0.63, p <0.001), the slope of posterior aortic wall displacement during early atrial emptying (r = 0.55, p <0.001), age (r = -0.50; p <0.001), pulmonary venous diastolic anterograde velocity (r = 0.41, p <0.01), and the systolic filling fraction (r = -0.43; p <0.01). By stepwise multiple linear regression analysis, left atrial fractional shortening and the pulmonary venous systolic filling fraction were the only determinants of the maximum oxygen consumption (multiple r = 0.70; p <0.001). Exercise capacity did not correlate with Doppler-derived transmitral indexes. Thus, in patients with HC, exercise capacity was determined by passive LV diastolic function, as assessed by the left atrial M-mode and Doppler-derived pulmonary venous flow velocities.

Survival after cardiac arrest or sustained ventricular tachycardia in patients with hypertrophic cardiomyopathy

OBJECTIVES

The aim of this study was to evaluate the survival of patients with hypertrophic cardiomyopathy (HCM) after resuscitated ventricular fibrillation or syncopal sustained ventricular tachycardia (VT/VF) when treated with low dose amiodarone or implantable cardioverter defibrillators (ICDs).

BACKGROUND

Prospective data on clinical outcome in patients with HCM who survive a cardiac arrest are limited, but studies conducted before the widespread use of amiodarone and/or ICD therapy suggest that over a third die within seven years from sudden cardiac death or progressive heart failure.

METHODS

Sixteen HCM patients with a history of VT/VF (nine male, age at VT/VF 19 +/- 8 years [range 10 to 36]) were studied. Syncopal sustained ventricular tachycardia/ventricular fibrillation occurred during or immediately after exertion in eight patients and was the initial presentation in eight. One patient had disabling neurologic deficit after VT/VF. Before VT/VF, two patients had angina, four had syncope and six had a family history of premature sudden cardiac death. After VT/VF all patients were in New York Heart Association class I or II, three had nonsustained VT during ambulatory electrocardiography and 11 had an abnormal exercise blood pressure response. After VT/VF eight patients were treated with low dose amiodarone and six received an ICD. Prophylactic therapy was declined by two patients.

RESULTS

Mean follow-up was 6.1 +/- 4.0 years (range 0.5 to 14.5). Cumulative survival (death or ICD discharge) for the entire cohort was 59% at five years (95% confidence interval: 33% to 84%). Thirteen (81%) patients were alive at last follow-up. Two patients died suddenly while taking low dose amiodarone, and one died due to neurologic complications of his initial cardiac arrest. Three patients had one or more appropriate ICD discharges during follow-up; the times to first shock after ICD implantation were 23, 197 and 1,124 days.

CONCLUSIONS

This study shows that patients with HCM who survive an episode of VT/VF remain at risk for a recurrent event. Implantable cardioverter defibrillator therapy appears to offer the best potential benefit regarding outcome.

Augmented exercise plasma noradrenaline with impaired chronotropic responsiveness in patients with hypertrophic cardiomyopathy

1. There is controversy regarding plasma catecholamine levels in patients with hypertrophic cardiomyopathy (HCM) and few data exist on serial plasma catecholamine measurements during exercise. The present study determined whether cardiovascular and plasma catecholamine responses to exercise were altered in patients with HCM. 2. Plasma noradrenaline (NA) and adrenaline were measured at rest, at the end of each stage during exercise and immediately and 5 min after submaximal treadmill exercise in 15 patients with non-obstructive HCM (13 males, two females; mean (+/- SEM) age 54 +/- 3 years) and in 15 age- and sex-matched controls. The ratio of the increment in heart rate (HR) divided by the increment in plasma NA during exercise (delta HR/delta NA) was used as an index of chronotropic sympathetic responsiveness to exercise. 3. Exercise duration was shorter (11.2 +/- 0.6 vs 8.7 +/- 0.6 min for control vs HCM, respectively; P < 0.01) and diastolic blood pressure was significantly higher at stages I and II of modified Bruce protocol HCM. 4. Resting plasma NA levels (149 +/- 17 vs 167 +/- 28 pg/mL for control vs HCM, respectively; NS) were not different, but plasma NA levels at stages I and II were significantly higher in HCM than in controls (243 +/- 26 vs 399 +/- 69 pg/mL (P < 0.05) and 308 +/- 30 vs 548 +/- 110 pg/mL (P < 0.05), respectively). 5. Peak plasma NA levels were not significantly higher in HCM than in controls (578 +/- 59 vs 918 +/- 184 pg/mL, respectively; NS). 6. The ratio delta HR/delta NA was significantly lower in HCM compared with control at stages I and II (0.49 +/- 0.10 vs 0.21 +/- 0.05 (P < 0.05) and 0.38 +/- 0.06 vs 0.20 +/- 0.05 (P < 0.05), respectively). There were no differences in plasma adrenaline responses during exercise between the two groups. 7. Patients with HCM had augmented plasma NA levels during submaximal exercise with a higher diastolic blood pressure response. Chronotropic sympathetic responsiveness was impaired during the early stages of exercise in patients with HCM.

Septal myectomy in hypertrophic obstructive cardiomyopathy: late results with stress echocardiography

BACKGROUND

This study was performed to assess the functional capacity of the survivors of septal myectomy for the treatment of hypertrophic obstructive cardiomyopathy in long-term follow-up as assessed by dobutamine stress echocardiography.

METHODS

Sixty-nine patients with hypertrophic obstructive cardiomyopathy underwent septal myectomy between 1975 and 1996. The mean age was 25.4 +/- 13.6 years (range, 6-58 years), and 10 of the patients were women. The early mortality was 4.3%. Hospital survivors (95.7%) were followed up for a mean of 43.8 +/- 28.7 months (range, 6-114 months).

RESULTS

The postoperative mean functional capacity of the group was 1.47 +/- 0.56. No late deaths were reported. Forty-nine patients (74.2%) were evaluated with standard echocardiographic techniques, and 29 (43.9%) patients underwent dobutamine stress echocardiography. There was a significant decrease in the thickness of the interventricular septum after surgery. The mean preoperative and postoperative septal thickness was 1.99 +/- 0.59 cm (range, 1.3-3.8 cm) and 1.55 +/- 0.41 cm (range, 0.96-2.8 cm), respectively (p < 0.004). The mean posterior wall thickness was significantly less than the preoperative value (p = 0.008) and the left ventricular end-diastolic diameter was slightly greater in the postoperative measurements, but the difference was not significant (p = 0.162). Postoperative left ventricular outflow systolic gradients were reduced significantly when compared with preoperative values (preoperative mean, 78.4 +/- 33.6 mm Hg, range, 50-212 mm Hg versus postoperative mean, 17.9 +/- 15.9 mm Hg: range, 0-40 mm Hg; p < 0.0001).

CONCLUSION

Septal myectomy for patients with hypertrophic obstructive cardiomyopathy is a safe procedure with excellent clinical and functional results in the long-term follow-up.

Left atrial function as a reliable predictor of exercise capacity in patients with recent myocardial infarction

STUDY OBJECTIVE

To examine the relation between left atrial (LA) function and exercise performance.

DESIGN AND SETTING

Retrospective study at a referral cardiopulmonary exercise laboratory in a university hospital.

PATIENTS

Forty-one patients with recent myocardial infarction.

INTERVENTIONS

M-mode echocardiography and cardiopulmonary exercise testing combined with radionuclide ventriculography.

MEASUREMENTS AND RESULTS

Hemodynamic measurements were obtained at rest and peak exercise. LA fractional shortening at rest was used as an index of global LA function. LA fractional shortening had fair correlations with peak oxygen consumption (r=0.67, p<0.01) and exercise duration (r=0.71, p<0.01). Although there were no significant relations between LA fractional shortening and hemodynamic measurements at rest, LA fractional shortening was positively related to peak cardiac output (r=0.61, p<0.01) and peak stroke volume (r=0.57, p<0.01), and negatively related to peak pulmonary arterial wedge pressure (r=-0.44, p<0.05). In addition, LA fractional shortening correlated significantly with an increase in left ventricular (LV) end-diastolic volume from rest to peak exercise (r=0.48, p<0.02), but did not correlate with the changes in ejection fraction and end-systolic volume during exercise. An increase in LV end-diastolic volume during exercise was significantly related to peak oxygen consumption (r=0.46, p<0.02), peak cardiac output (r=0.60, p<0.01), and peak stroke volume (r=0.53, p<0.01), whereas the changes in ejection fraction and end-systolic volume during exercise were not related to these indexes.

CONCLUSIONS

Exercise capacity and LV performance during exercise were mainly dependent on LV diastolic filling rather than systolic contraction during exercise. LA fractional shortening at rest reflected LV diastolic filling during exercise and, therefore, predicted cardiac output and stroke volume responses to exercise and exercise capacity in patients with recent myocardial infarction.

Effects of left ventricular peak filling rate on exercise capacity 3 to 6 weeks after acute myocardial infarction

STUDY OBJECTIVES

To investigate the importance of early left ventricular (LV) diastolic filling on maintenance of exercise performance, we examined peak filling rate and its relation to exercise capacity during upright bicycle exercise in patients with recent myocardial infarction.

DESIGN

Retrospective analysis of data of cardiopulmonary exercise testing characteristics in patients with recent myocardial infarction.

SETTING

Coronary care unit in a university hospital.

PATIENTS

Fifty-one patients 3 to 6 weeks after acute myocardial infarction.

INTERVENTIONS

Upright bicycle exercise using a symptom-limited graded exercise protocol.

MEASUREMENTS AND RESULTS

Peak filling rate increased significantly from 1.55 +/- 0.52 at rest to 3.43 +/- 1.1 end-diastolic volume per second at peak exercise. Despite no significant relation between peak filling rate at rest and peak oxygen consumption, peak filling rate at peak exercise correlated significantly with peak oxygen consumption (r = 0.50; p < 0.002), stroke volume (r = 0.51; p < 0.002), and cardiac output (r = 0.56; p < 0.002) at peak exercise. Although both end-systolic and end-diastolic volumes increased from rest to peak exercise, the increases in end-systolic volume correlated inversely with the changes in peak filling rate during exercise (r = -0.45; p < 0.02), but the increases in end-diastolic volume did not.

CONCLUSIONS

During maximal upright bicycle exercise, exercise capacity and exercise hemodynamic responses were mainly dependent on early LV diastolic filling, and preserved LV systolic contraction, resulting in a cardiac suction effect following early diastole, seemed to have an important role in the enhancement of early LV diastolic filling in patients with recent myocardial infarction.

Importance of left ventricular diastolic function on maintenance of exercise capacity in patients with systolic dysfunction after anterior myocardial infarction

To investigate the role of left ventricular (LV) diastolic function in the maintenance of exercise capacity in patients with systolic dysfunction, symptom-limited cardiopulmonary exercise testing combined with radionuclide ventriculography was performed in 24 patients with an LV ejection fraction < 35% after anterior myocardial infarction. The ratio of pulmonary artery wedge pressure (PAWP) to LV end-diastolic volume (EDV), an index of global diastolic function, correlated significantly with peak oxygen consumption at peak exercise (r = -0.55; p = 0.006), whereas ejection fraction at peak exercise did not. The change in PAWP/EDV ratio from rest to peak exercise was related to the increases in stroke volume (r = -0.54; p = 0.006) and cardiac output (r = -0.51; p = 0.01) during exercise, but the change in ejection fraction was not. Resting hemodynamics did not differ between patients with preserved exercise capacity (group 1, n = 8) and those with exercise impairment (group 2, n = 16). At peak exercise, stroke volume, cardiac output, and EDV were significantly higher, and PAWP and PAWP/EDV ratio were significantly lower in group 1 than in group 2, but ejection fraction and end-systolic volume were similar in both groups. Although the incidences of hypertension, LV hypertrophy, and infarct-related coronary artery lesions did not differ between the two groups, group 2 had a significantly higher incidence of non-infarct-related coronary artery lesions than group 1 (p < 0.05). Thus in patients with LV systolic dysfunction after anterior myocardial infarction, the major cause of exercise impairment and failure to increase LV performance during exercise was diastolic dysfunction associated with the presence of non-infarct-related coronary artery lesions with the potential for exercise-induced ischemia of the noninfarcted areas.

Dual-chamber pacing for cardiomyopathies: a 1996 clinical perspective

Implantation of a permanent pacemaker is an accepted mode of therapy for symptomatic bradyarrhythmias. Application of pacemaker technology for the treatment of cardiomyopathies has generated considerable interest and enthusiastic support in recent years. In both hypertrophic cardiomyopathy and dilated cardiomyopathy, dual-chamber pacing has been shown to decrease symptoms and improve hemodynamics; however, not all patients will benefit from dual-chamber pacing. Technical considerations must be acknowledged in order to obtain optimal benefit with dual-chamber pacing. In addition, other more accepted therapies are available for patients with symptomatic cardiomyopathies. The purposes of this article are to review critically the current literature on the use of dual-chamber pacemakers in patients with either hypertrophic or dilated cardiomyopathy and to provide a clinical perspective based on current knowledge.

Functional capacity before and after cardioversion of atrial fibrillation: a controlled study

OBJECTIVE

To evaluate the effect of cardioversion on peak oxygen consumption (peak VO2) in patients with long-standing atrial fibrillation, to assess the importance of underlying heart disease with respect to the response to exercise, and to relate functional capacity to long-term arrhythmia outcome.

DESIGN

Prospective controlled clinical trial.

SETTING

Tertiary referral centre.

PATIENTS

63 consecutive patients with chronic atrial fibrillation accepted for treatment with electrical cardioversion. Before cardioversion all patients were treated with digoxin, verapamil, or a combination of both to attain a resting heart rate < or = 100 beats per minute.

INTERVENTIONS

Electrical cardioversion.

MAIN OUTCOME MEASURES

Peak VO2 measured before and 1 month after electrical cardioversion to compare patients who were in sinus rhythm and those in atrial fibrillation at these times. Maintenance of sinus rhythm for a mean follow up of 19 (7) months.

RESULTS

Mean (1SD) peak VO2 in patients in sinus rhythm after 1 month (n = 37) increased from 21.4 (5.8) to 23.7 (6.4) ml/min/kg (+11%, P < 0.05), whereas in patients with a recurrence of atrial fibrillation 1 month after cardioversion (n = 26) peak VO2 was unchanged. In patients who were in sinus rhythm both those with and without underlying heart disease improved, and improvement was not related to functional capacity or left ventricular function before cardioversion. Baseline peak VO2 was not a predictive factor for long-term arrhythmia outcome.

CONCLUSION

Restoration of sinus rhythm improved peak VO2 in patients with atrial fibrillation, irrespective of the presence of underlying heart disease. Peak VO2 was not a predictive factor for long-term arrhythmia outcome after cardioversion of atrial fibrillation. These findings suggest that cardioversion is the best method of improving functional capacity in patients with atrial fibrillation, whether or not they have underlying heart disease and whatever their functional state.