Heterogeneous mechanisms of pulmonary congestion in hypertrophic cardiomyopathy unmasked by comprehensive exercise stress echocardiography

Background

B-lines detected by lung ultrasound (LUS) during exercise stress echocardiography (ESE), indicating pulmonary congestion, are present in 1 out of 3 patients with hypertrophic cardiomyopathy (HCM).

Aim

To assess the functional and anatomical correlates of exercise B-lines in HCM.

Methods

We enrolled 191 HCM patients (age 53±15 years, 123 males) consecutively referred for ESE (treadmill in 74, bicycle in 117 patients) in 11 quality-controlled centers from 8 countries. ESE assessment at rest and peak stress included: left ventricular (LV) outflow tract gradient, left atrial (LAVi) and LV end-diastolic volume index (EDVi), mitral regurgitation (MR, score from 0 to 3); E/e'; systolic pulmonary arterial pressure (SPAP) and LV force (LV outflow tract gradient+systolic blood pressure/LV end-systolic volume). B-lines at rest and at peak exercise were assessed by LUS with the 4-site simplified scan. B-lines positivity was considered if the sum of detected B-lines was ≥2.

Results

LUS was feasible in all subjects. B-lines were present in 55 (29%) patients during stress. When compared to patients without stress B-lines (n=136), patients with B-lines (n=55) at peak exercise had lower peak EDVi (43±17 vs 52±18 ml/m2, p=0.003) higher peak E/e' (16±6 vs 12±5, p<0.001), increase in MR (34 vs 12%, p=0.001), greater stress LAVi (43±14 vs 37±14 ml/m2, p=0.003) and stress SPAP (56±18 vs 40±12 mm Hg p<0.0001): see Figure. Among baseline parameters, the number of B-lines (OR: 7.53, 95% CI 1.21–46.72 p=0.03), LAVi (OR: 1.05, 95% CI 1.00–1.09 p=0.04), and LV force (OR: 1.36, 95% CI 1.04–1.79 p=0.03) were the independent predictors of exercise pulmonary congestion.

Conclusion

HCM patients with pulmonary congestion on exercise show different, and not mutually exclusive mechanisms of diastolic dysfunction and worsening mitral regurgitation. These different hemodynamic mechanisms may require personalized therapeutic actions beyond a pulmonary decongestion therapy with diuretics.

Funding Acknowledgement

Type of funding sources: None.

Clinical, functional and prognostic correlates of excess left ventricular force in hypertrophic cardiomyopathy

Background

Excess force generation during myocardial contraction represents a cardinal feature of hypertrophic cardiomyopathy (HCM).

Purpose

To evaluate the anatomical, functional and prognostic correlates of left ventricular (LV) force in HCM.

Methods

We prospectively recruited a consecutive sample of 408 HCM patients with LV ejection fraction (EF) >50%, referred for baseline transthoracic echocardiography in 2 primary HCM centers in Hungary and Italy between 1999 and 2021. LV force was calculated as LV outflow tract gradient+systolic blood pressure/LV end-systolic volume. Patients were followed for a median of 107 months (IQ range, 58–158 months), the study endpoint was all-cause mortality.

Results

Mean LV force was 6.0±4.6 mm Hg/ml. Receiver-operating characteristic analysis identified 7.5 mm Hg/ml the best cut-off value to predict mortality. LV force >7.5 mm Hg/ml was present in 86 patients (21%), more frequently in women (58 vs 27%, p<0.0001), more often in patients with diabetes (16 vs 6%, p=0.003), beta-blocker (81 vs 58%, p<0.0001), calcium channel-blocker (19 vs 9%, p=0.012) and diuretic therapy (19 vs 8%, p=0.004), compared to patients with LV force ≤7.5 mm Hg/ml. Patients with excess LV force had more advanced NYHA class (1.8±0.7 vs 1.4±0.7, p=0.0001), greater left atrial diameter [(LAd), 46.7±6.6 vs 43.0±7.2 mm, <0.0001], LV maximal wall thickness (23.2±5.5 vs 21.6±5.5 mm p=0.01), LV EF (74.6±6.4 vs 67.0±6.8%, <0.0001), mitral regurgitation grade (1.2±0.7 vs 0.7±0.7, p<0.0001) and E/e' (10.3±5.0 vs 7.8±5.0, p=0.005). During follow-up 43 deaths occurred. All-cause death was more frequent in patients with excess LV force (21 vs 8%, p<0.0001). At multivariable Cox regression analysis, excess LV force was an independent predictor of mortality (HR 2.9, 95% CI 1.14–7.26, p=0.025) independent of age (HR 1.03, 95% CI 1.00–1.05, p=0.022) and LAd (HR 1.07, 95% CI 1.02–1.14, p=0.005).

Conclusion

LV force with a threshold of 7.5 mm Hg/ml, independently predicts adverse outcome in patients with HCM and preserved systolic function. Excess LV force generation is associated with female sex, diabetes, NYHA class, medications, LAd, LV wall thickness, EF, mitral regurgitation grade and E/e'.

Funding Acknowledgement

Type of funding sources: None.

Adverse prognostic value of supernormal left ventricular force noninvasively assessed by resting transthoracic echocardiography in hypertrophic cardiomyopathy

Funding Acknowledgements

Type of funding sources: None.

OnBehalf

Stress Echo 2030 study group of the Italian Society of Echocardiography and Cardiovascular Imaging (SIECVI).

Background The excessive cross-bridging of cardiac myosin and actin, resulting in increased left ventricular (LV) force development, is one of the biomechanical abormalities inhypertrophic cardiomyopathy (HCM).

Purpose

To assess the prognostic value of increased LV force development at rest in patients with HCM

Methods

We enrolled 918 HCM patients (age 48 ± 16 years, 502 males, New York Heart Association I or II, Class III in 48 patients, 6% and with LVOTG >30 mmHg in 211patients, 23%) with ejection fraction (EF) ≥50%, referred for rest transthoracic echocardiography (TTE) in 10 quality-controlled labs from 7 countries (Belgium, Hungary, Italy, Portugal, Serbia, Spain, Brazil). The maximal wall thickness was 21 ± 5 mm. TTE assessment included left ventricular outflow tract gradient (LVOTG, mmHg), EF (%), and LV force (systolic arterial pressure + LVOTG/LV endsystolic volume assessed with 2-D, mmHg/mL). All patients were followed-up. An age- and gender matched control group of 95 healthy subjects was also evaluated.

Results.  Compared to normals, HCM showed higher values of EF (68 ± 8 vs 65 ± 5%, p < 0.001) and force (7.2 ± 5.5 vs 4.0 ± 1.8 mmHg/mL, p < 0.001). At a median follow-up of 94 months [interquartile range 40-140 months], 95 all-cause deaths occurred. Mortality was significantly increased in the force highest quartile compared to other quartiles (see figure). At multivariable Cox analysis, increased Force (highest quartile >8.5 mmHg/mL hazard ratio= 2.189 95% CI = 1.095-4.377, p = 0.027 and the intermediate quartile: Force 5.7-8.5 mmHg/mL hazard ratio= 2.525 95% CI = 1.2205.228, p = 0.013) were independent predictors of mortality with age (hazard ratio= 1.065 95% CI = 1.047-1.084, p < 0.001) and maximal wall thickness (hazard ratio= 1.094, 95% CI = 1.055-1.135, p < 0.001). At univariate analysis neither LVOTG (hazard ratio= 1.430, 95% CI = 0.920-2.222, p = 0.112) nor quartiles of EF (hazard ratio= 1.497, 95% CI = 0.868-2.582, p = 0.147) were significant.

Conclusion

HCM patients with preserved baseline LV function and higher values of resting LV force ("too good to be normal") show a worse survival, highlighting the dark prognostic side of an excess of force. The hypercontractile phenotype possibly indicates an increased activity of myosin resulting in increased force production at the sarcomere and cellular levels that propagates at the whole-organ level with unfavorable long-term effects on outcome.

Figure

Mortality rate based on quartiles of resting LV Force in HCM. Abstract Figure. Mortality rate

Comprehensive stress echocardiography in hypertrophic cardiomyopathy

Funding Acknowledgements

Type of funding sources: None.

OnBehalf

Stress Echo 2020 study group of the Italian Society of Echocardiography and Cardiovascular Imaging

Background

Stress echocardiography (SE) in hypertrophic cardiomyopathy (HCM) has more to offer beyond dynamic left ventricular outflow obstruction (LVOTO) to capture the functional heterogeneity of the disease.

Objectives

To determine the feasibility of comprehensive SE in HCM.

Methods

We prospectively enrolled 235 HCM patients (age = 48 ± 15 years, 113 men) assessed with exercise stress echocardiography (ESE) in 4 centers. ESE modality was semi-supine bicycle in 29 patients in one center, and treadmill in 206 (followed by same-day, same session, adenosine for step D) in another centers. During SE, we assessed stress-induced new regional wall motion abnormalities (RWMA, step A), coronary flow velocity reserve (CFVR) in left anterior descending coronary artery with Doppler (step D) by semi-supine exercise or adenosine, heart rate reserve (peak/rest heart rate) for EKG-based step E, mitral regurgitation (MR) flow for step F, and LVOTO (step G for gradient). A comprehensive SE score was generated from 0 (all parameters normal) to 5 (all abnormal).

Results

 Technical success rate was 100% for all steps, except step D (80% with semi-supine, 100% with adenosine after treadmill) and F (232/235, 99%).  Extra-analysis time was < 3 minutes for steps A + D + E + F + G. Rate of abnormal results ranged from 73% for step E (peak/rest heart rate reserve < 1.80) to 1% for step A (inducible RWMA), with intermediate values for step D (CFVR < 2.0, 44%), step F (at least moderate MR, 32%) and step G (LVOTG > 50 mm Hg, 26%): see figure. SE score was 0 in 14 pts (6%), 1 or 2 in 202 patients (86%) and ≥ 3 in 19 patients (8%).

Conclusions

 Comprehensive SE is feasible in HCM with single stress (semi-supine exercise) or hybrid treadmill exercise followed by adenosine for step D. Phenotyping of the multiform manifestations of HCM with a personalized functional blueprint is now possible. Abstract Figure.

Pulmonary congestion during exercise stress echocardiography in hypertrophic cardiomyopathy

Background

B-lines detected by lung ultrasound (LUS) indicate pulmonary congestion during exercise stress echo (ESE).

Aim

To assess B-lines during ESE in hypertrophic cardiomyopathy (HCM).

Methods

We enrolled 110 HCM patients (age 52±16 years, 74 males) referred for ESE (treadmill in 39, semi-supine bicycle in 71 patients) in 10 quality-controlled centers from 8 countries (Belgium, Brazil, Bulgaria, Hungary, Italy, Portugal, Serbia, Spain). ESE assessment included: left ventricular outflow tract gradient (LVOTG); mitral regurgitation (MR, score from 0 to 3); E/e'; systolic pulmonary arterial pressure (SPAP, from tricuspid regurgitant jet velocity); end-diastolic volume (EDV); left atrial volume (LAV). B-lines were assessed by LUS with the 4-site simplified scan, each site scored from 0 (normal A-lines) to 10 (coalescing B-lines). The positivity criterion was a B-line score stress ≥2 points.

Results

LUS was feasible in all subjects, with additional scanning and analysis time <1 minute for each stage (rest and peak stress). B-lines were present in 13 patients at rest and in 33 during stress (12 vs 30%, p<0.001). When compared to patients without stress B-lines (Group 2, n=77), patients with B-lines (Group 1) showed higher values of change from rest to stress (Δ) in LVOTG (Group 1= 39±54 vs Group 2= 21±24 mm Hg, p=0.015) and ΔMR grade (Group 1= 0.7±0.8 vs Group 2= 0.1±0.5, p<0.001), more frequent peak stress E/e' ≥15 (Group 1=61% vs Group 2=27%, p=0.007), lower peak EDV (Group 1= 86±35 vs Group 2= 102±33 ml, p=0.039) and higher peak SPAP (Group 1= 60±21 vs Group 2= 39±12 mm Hg, p<0.001): see figure. At multivariable logistic regression analysis, presence of stress B-lines was predicted by ΔMR grade (odds ratio: 3.96, 95% CI 1.46–10.71) and stress E/e' ≥15 (odds ratio: 4.95, 95% CI 1.24–19.70).

Conclusion

B-lines are found in about 1 of 10 HCM patients at rest and in 1 of 3 during ESE. Acute backward heart failure during exercise can recognize multiple mechanisms in HCM, and ESE can help to capture this heterogeneity.

Funding Acknowledgement

Type of funding sources: None. Functional correlates of stress B-lines

Clinical, functional and prognostic correlates of blunted heart rate reserve during exercise stress echocardiography in hypertrophic cardiomyopathy

Funding Acknowledgements

Type of funding sources: None.

Background

Blunted heart rate reserve (HRR) during exercise is associated with cardiac autonomic dysfunction and poor outcome.

Purpose

To evaluate the anatomical, functional and prognostic correlates of HRR during exercise stress echocardiography (ESE) in hypertrophic cardiomyopathy (HCM).

Methods

We prospectively recruited a consecutive sample of 121 HCM patients [age 47 ± 13 years, 67 males; NYHA class 1.7 ± 0.7; left ventricular (LV) ejection fraction 71 ± 9 %; LV maximal wall thickness 24 ± 5 mm; 58 (48%) with LV outflow tract obstruction (LVOTO, gradient ≥ 50 mmHg) at rest] who underwent semi-supine bicycle ESE from January 2006 to September 2019. HRR was calculated as the peak/rest heart rate (HR) ratio. All patients were followed-up for a median of 7.5 years.

Results

HR was 68 ± 11 bpm at rest and 105 ± 19 bpm at peak stress. Receiver-operating characteristic analysis was used to determine the best cut-off value of HRR (≤ 1.48, blunted) to predict all-cause death. A blunted HRR was present in 52 patients (43 %, Group 1). Patients with blunted HRR had more frequently hypertension (Group 1= 41/52 vs Group 2= 40/69, 79 vs 58 %, p = 0.019), resting systolic anterior motion of the mitral valve [(SAM) , Group 1= 41/52 vs Group 2= 40/69, 79 vs 58 %, p = 0.019] and rest LVOTO (Group 1= 31/52 vs Group 2= 27/69, 60 vs 39 %, p = 0.029).  Patients in Group 1 had larger left atrial diameter (48.8 ± 6.5 vs 46.5 ± 7.6, p = 0.076), lower LV end-diastolic [(EDD) , 44.8 ± 4.6 vs 46.7 ± 4.6 mm p = 0.02] and LV end-systolic diameter [(ESD), 25.2 ± 5.3 vs 27.6 ± 5.5 mm p = 0.02] at rest. Patients in Group 1 had higher NYHA class (1.9 ± 0.6 vs 1.6 ± 0.7, p = 0.009), resting HR (71.5 ± 11.4 vs 64.6 ± 10.6 bpm p < 0.001), and shorter total exercise time (6.3 ± 3.1 vs 9.1 ± 2.8 min, p < 0.001) compared to patients in Group 2.

During the follow-up, 13 patients died. All-cause death was observed in 10/52 patients of Group 1 and 3/69 patients of Group 2 (19 vs 4 %, p < 0.05). Cox multivariate regression survival analysis revealed that HRR ≤ 1.48 (Hazard ratio 3.7, 95% CI 0.96-14.5, p = 0.048) and left atrial diameter (Hazard ratio 1.15, 95% CI 1.04-1.28, p = 0.003) were independent predictors of all-cause mortality, either on or off beta-blocker therapy.

Conclusion

HRR is a simple non-imaging biomarker of cardiac autonomic function and is frequently abnormal in HCM. The blunted increase in frequency is associated with NYHA functional class, exercise time, rest HR, rest LVOTO, SAM, LV EDD and ESD. HRR independently predicts survival in HCM. The lower the HRR, the worse the outcome.

Abstract Figure.

Prognostic value of reduced heart rate reserve during exercise stress-echocardiography in hypertrophic cardiomyopathy

Background

Heart rate reserve (HRR) during exercise evaluates chronotropic incompetence and is a prognostically important marker of cardiac autonomic dysfunction, additive to regional wall motion abnormalities (RWMA) in patients with coronary artery disease.

Objectives

To assess determinants and prognostic value of HRR in patients with hypertrophic cardiomyopathy (HCM).

Methods

From 1998 to 2019, we enrolled 774 HCM patients (age = 48.8±15.9 years, 410 men) with exercise stress echocardiography (ESE) in 10 certified centres of the international stress echo network. During ESE we assessed: left ventricular outflow tract obstruction (LVOTO, significant when >50 mmHg); RWMA; HRR (peak/ rest heart rate), 344 in beta-blockers therapy (44.4%). Patients were followed for a median 49 months (IQ range, 25–78 months). The study end-point was all-cause mortality.

Results

During ESE, we observed stress-induced RWMA in 42 (5.4%) and LVOTO in 248 (33%); HRR was 1.92.±0.41. There were no difference in patients with normal and abnormal HRR with and without beta-blockers therapy (147, 41.1% vs 211, 58.9%, p=0.079). During follow-up, 43 deaths occurred. Beta blockers therapy in univariate analysis did not have prognostic role (HR 1.105, 95% CI 0.602–2.028, p=0.768). The lowest HRR quartile (≤1.62) had a 10-fold higher 6-year death rate (10.9%) than the highest quartile (>2.16, 1.04%): see figure. At multivariable analysis, lowest HRR quartile (HR 2.074, 95% CI 1.082–6.773, p=0.034), age (HR 1.045, 95% CI 1.014–1.077, p=0.004), maximal wall thickness (HR 1.137, 95% CI 1.054–1.226, p=0.001), stress-induced RWMA s(HR 4.289, 95% CI 1.733–10.615, p=0.002) and ≥ moderate mitral regurgitation at rest (HR 3.127, 95% CI 1.507–6.488, p=0.002) predicted death.

Conclusions

A blunted HRR during ESE predicts adverse outcome independent of inducible RWMA in HCM patients. Autonomic dysfunction deserves consideration as a potential therapeutic target in this disease.

Figure 1

Funding Acknowledgement

Type of funding source: None

Prognostic role of coronary flow velocity reserve in hypertrophic cardiomyopathy

Background

A reduction in coronary flow velocity reserve (CFVR) related to coronary microvascular dysfunction is a major mechanism for ischemia in hypertrophic cardiomyopathy (HCM).

Hypothesis

To assess the functional correlates and prognostic value of CFVR during stress echocardiography (SE) in HCM.

Methods

We enrolled 201 HCM patients (age 51±14 years, 105 male, 52%; maximal wall thickness: 18±3 mm) studied with CFVR during exercise (n=33, 16.4%), dipyridamole (n=89, 44.3%) or adenosine (n=79, 39.3%) SE in 6 certified centers. CFVR was assessed using pulsed wave Doppler sampling in left anterior descending coronary artery. All patients completed the clinical follow-up.

Results

During SE mean value of CFVR was 2.11±0.46. No patients showed regional wall motion abnormalities during stress. LV outflow tract obstruction (LVOTO) was present in 34 (16.9%) patients at rest and in 47 (23.4%) at peak stress. CFVR was inversely related to age (r=−0.229, p=0.001) and maximal wall thickness (r=−0.197, p=0.031). During a median follow-up of 26 months (IQ range: 12–48 months), 75 events in 63 patients occurred: 10 deaths, 33 new hospital admission for acute heart failure, 8 sustained ventricular tachycardias and 24 atrial fibrillations. Patients in the lowest tertile (≤1.88) showed the worse prognosis with higher incidence of follow-up events compared to median tertile (1.89–2.29) and highest tertile (≥2.30) (see figure). At multivariable analysis, NYHA functional class (HR: 2.234, 95% CI: 1.398–3.517, p=0.001), presence of LVOTO at rest (HR: 2.958, 95% CI: 1.074–3.570, p=0.028) and lowest tertile of CFVR (HR: 2.144, 95% CI: 1.126–4.081, p=0.011) were the independent predictors of follow-up events.

Conclusions

In HCM patients, reduction in CFVR is associated to a clearly worse outcome. The spectrum of prognostic stratification is expanded if the response is titrated according to a continuous scale.

Figure 1

Funding Acknowledgement

Type of funding source: None

Sequential metabolic phases as a means to optimize cellular output in a constant environment

Temporal changes of gene expression are a well-known regulatory feature of all cells, which is commonly perceived as a strategy to adapt the proteome to varying external conditions. However, temporal (rhythmic and non-rhythmic) changes of gene expression are also observed under virtually constant external conditions. Here we hypothesize that such changes are a means to render the synthesis of the metabolic output more efficient than under conditions of constant gene activities. In order to substantiate this hypothesis, we used a flux-balance model of the cellular metabolism. The total time span spent on the production of a given set of target metabolites was split into a series of shorter time intervals (metabolic phases) during which only selected groups of metabolic genes are active. The related flux distributions were calculated under the constraint that genes can be either active or inactive whereby the amount of protein related to an active gene is only controlled by the number of active genes: the lower the number of active genes the more protein can be allocated to the enzymes carrying non-zero fluxes. This concept of a predominantly protein-limited efficiency of gene expression clearly differs from other concepts resting on the assumption of an optimal gene regulation capable of allocating to all enzymes and transporters just that fraction of protein necessary to prevent rate limitation. Applying this concept to a simplified metabolic network of the central carbon metabolism with glucose or lactate as alternative substrates, we demonstrate that switching between optimally chosen stationary flux modes comprising different sets of active genes allows producing a demanded amount of target metabolites in a significantly shorter time than by a single optimal flux mode at fixed gene activities. Our model-based findings suggest that temporal expression of metabolic genes can be advantageous even under conditions of constant external substrate supply.

Prognostic significance of the dobutamine echocardiography test in idiopathic dilated cardiomyopathy

Dobutamine stress echo provides potentially useful information on idiopathic dilated cardiomyopathy (IDC). From February 1, 1997, to October 1, 1999, 186 patients (131 men and 55 women, mean age 56 +/- 12 years) with IDC, ejection fraction <35%, and angiographically normal coronary arteries were studied by high-dose (up to 40 micro/kg/min) dobutamine echo in 6 centers, all quality controlled for stress echo reading. In all patients, wall motion score index (WMSI) (from 1 = normal to 4 = dyskinetic in a 16- segment model of the left ventricle) was evaluated by echo at baseline and peak dobutamine. One hundred eighty-four patients were followed up (mean 15 +/- 13 months) and only cardiac death was considered as an end point. There were 29 cardiac deaths. Significant parameters for survival prediction at univariate analysis are: DeltaWMSI (chi-square 20.1; p <0.0000), New York Heart Association (NYHA) class (chi-square 17.57; p <0.0000), rest ejection fraction (chi-square 10.41; p = 0.0013), angiotensin-converting enzyme inhibitors (chi-square 8.23; p = 0.0041), and hypertension (chi-square 8.08, p = 0.0045). In the multivariate stepwise analysis only DeltaWMSI and NYHA were independent predictors of outcome (DeltaWMSI = hazard ratio 0.02, p < 0.0000; NYHA class = hazard ratio 3.83, p < 0.0000). Kaplan-Meier survival estimates showed a better outcome for patients with a large inotropic response (DeltaWMSI > or =0.44, a cutoff identified by receiver-operating characteristic curves analysis) than for those with a small or no myocardial inotropic response to dobutamine (93.6% vs 69.4%, p = 0.00033). Thus, in patients with IDC, an extensive contractile reserve identified by high-dose dobutamine stress echocardiography is associated with a better survival.