Is Functional Capacity Related to Left Atrial Contractile Function in Nonobstructive Hypertrophic Cardiomyopathy?

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.

Left atrial remodelling may predict exercise capacity in obstructive sleep apnoea patients

BACKGROUND

Left atrial volume (LAV) and LA deformation has been proposed as a good marker of exercise performance in patients with diastolic dysfunction (DD). As DD is more prevalent in obstructive sleep apnoea (OSA) we aimed to evaluate the influence of LAV and LA deformation parameters on exercise performance in varying severity of OSA.

MATERIALS AND METHODS

OSA was diagnosed after polysomnography. Fifty-five OSA patients were enrolled in the study. OSA patients were divided into two groups with apnoea-hypopna-index (AHI) > 30 and <30. LAV was calculated. LA strain and LA strain rates were assessed with speckle tracking echocardiography (STE). Exercise capacity was evaluated by treadmill exercise test.

RESULTS

MET values were lower in group II compared to group I (p < .05). Echocardiographic findings: Comparison within groups: In both groups E/E', LA stain, LA strain rate S and LA strain rate E were higher after exercise than before (p < .05). In group I LA strain rate A was higher after exercise than before (p < .05). Comparison between groups: LA strain, LA strain rate S, LA strain rate E and LA strain rate A were lower and E/E' and LAVI were higher in group II compared to group I before and after exercise (p < .05). Correlation with METs: AHI, LVEDV, E/E' and LAVI were negatively and LA strain was positively correlated with METs (p < .05).

CONCLUSIONS

Left ventricular diastolic dysfunction is more prevalent in severe OSA and is associated with impaired exercise performance. Additionally, LA remodelling may predict exercise capacity in this subgroup of patients.

Clinical significance of left atrial volume in clinical outcomes of heart transplant recipients

Background

Left atrial volume (LAV) is surgically kept enlarged in heart transplant (HT) recipients. On the other hand, LAV has been known an independent predictor of various cardiovascular diseases and is associated with exercise capacity of HT recipients. Thus, we evaluated the hypothesis that LAV is still associated with clinical outcomes in HT recipients whose left atria are artificially enlarged.

Methods

Clinical outcomes over 5 years after HT were retrospectively evaluated in 35 HT recipients who had a LAV measurement with echocardiography at 1 year after HT at the University of Cincinnati Medical Center. The LAV was derived from a stacked disc method using apical 4 and 2 chamber views.

Results

The average LAV normalized to body surface area was 38.3 ± 9.9 ml/m² (mean ± SD) at 1 year after HT. Two deaths and one drop-out occurred during 5-year follow up. A total of 552 cardiac symptom-related hospitalizations occurred in the recipients. The average time to first hospitalization was 166 ± 279 days and average number of hospitalizations of each recipient was 15 ± 16. The indexed LAV failed to correlate with the time to first hospitalization and number of hospitalizations of each recipient (Spearman’s p-value; 0.141 and 0.519 respectively). When the patients were divided to groups of large LAV (n = 17) and small LAV (n = 18) using the cut off value of the mean LAV, no significant difference was noted in mortality, hospitalization, and new onset of atrial fibrillation between the groups.

Conclusions

Although our study is limited by a retrospective study design and relatively small number of patients, our results implicate that LAV is not significantly associated with clinical outcomes in HT recipients over 5 years after HT.

Does left atrial volume affect exercise capacity of heart transplant recipients?

BACKGROUND

Heart transplant (HT) recipients demonstrate limited exercise capacity compared to normal patients, very likely for multiple reasons. In this study we hypothesized that left atrial volume (LAV), which is known to predict exercise capacity in patients with various cardiac pathologies including heart failure and hypertrophic cardiomyopathy is associated with limited exercise capacity of HT recipients.

METHODS

We analyzed 50 patients [age 57 ±2 (SEM), 12 females] who had a post-HT echocardiography and cardiopulmonary exercise test (CPX) within 9 weeks time at clinic follow up. The change in LAV (ΔLAV) was also computed as the difference in LAV from the preceding one-year to the study echocardiogram. Correlations among the measured parameters were assessed with a Pearson's correlation analysis.

RESULTS

LAV (n = 50) and ΔLAV (n = 40) indexed to body surface area were 40.6 ± 11.5 ml·m-2 and 1.9 ± 8.5 ml·m-2·year-1, data are mean ± SD, respectively. Indexed LAV and ΔLAV were both significantly correlated with the ventilatory efficiency, assessed by the VE/VCO2 slope (r = 0.300, p = 0.038; r = 0.484, p = 0.002, respectively). LAV showed a significant correlation with peak oxygen consumption (r = -0.328, p = 0.020).

CONCLUSIONS

Although our study is limited by a retrospective study design and relatively small number of patients, our findings suggest that enlarged LAV and increasing change in LAV is associated with the diminished exercise capacity in HT recipients and warrants further investigation to better elucidate this relationship.

Use of bicycle exercise echocardiography for unexplained exertional dyspnea

Unexplained exertional dyspnea is a common and perplexing clinical problem. Myocardial ischemia and left ventricular systolic dysfunction are important cardiac causes, but are often not detected in these patients. Recently, exercise-induced left ventricular diastolic dysfunction and exercised-induced pulmonary hypertension have emerged as common alternative mechanisms. While conventional exercise treadmill echocardiography effectively diagnoses left ventricular systolic dysfunction and myocardial ischemia, it has limited ability to detect exercise-induced diastolic dysfunction or pulmonary hypertension. The latest advances in exercise echocardiography, including utilization of tissue Doppler imaging and harmonic imaging, make noninvasive evaluation of both conventional and alternative cardiac causes of exertional dyspnea possible. These advancements, when coupled with newly designed supine exercise platforms for bicycle exercise echocardiography (BE), facilitate the detection of exercise-induced diastolic dysfunction and pulmonary hypertension. Moreover, BE using supine ergometry additionally permits the dynamic evaluation of valvular function and interatrial shunting and detection of pulmonary arteriovenous fistula, uncommon but important causes of unexplained exertional dyspnea. Therefore, we propose that because of its superior diagnostic capabilities, BE should be included as part of a comprehensive cardiac evaluation of patients with unexplained exertional dyspnea.

Significance of left atrial contractile function in asymptomatic subjects with hereditary hemochromatosis

Patients with hereditary hemochromatosis (HH) have been reported to develop diastolic functional abnormalities detectable by echocardiography, but it is unknown whether these occur in asymptomatic subjects. Thus, this study tested whether echocardiographic left ventricular (LV) relaxation abnormalities are detectable in subjects with asymptomatic HH. Forty-three asymptomatic subjects with HH (C282Y homozygosity in the HFE gene) and 21 age- and gender-matched control subjects without known HFE mutations underwent echocardiography with comprehensive diastolic functional evaluations. Subjects with HH were in New York Heart Association functional class I and consisted of 22 newly diagnosed patients (group A) and 21 chronically phlebotomized subjects with stable iron levels (group B). Group A subjects showed significant iron overload compared with group B subjects and controls (group C) (ferritin 1,164 +/- 886 [p <0.05 vs groups B and C], 128 +/- 262, and 98 +/- 76 microg/L and transferrin saturation 79 +/- 19% [p <0.05 vs groups B and C], 42 +/- 21%, and 26 +/- 10% for groups A, B, and C, respectively). Echocardiographic evaluation revealed (1) no statistically significant abnormalities of Doppler LV relaxation in HH groups; (2) significant augmentation of atrial contractile function in subjects with HH compared with controls, which was not correlated with iron levels and treatment status; and (3) the preservation of overall LV systolic function in HH groups. In conclusion, the results of this study suggest that the augmentation of atrial contraction appears to be an early detectable echocardiographic cardiac manifestation of abnormal diastolic function in asymptomatic subjects with HH, which may reflect undetectable subclinical LV relaxation abnormalities.

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

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