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Research Article

Comparative hemodynamics of ATTR and AL amyloidosis with exercise-induced pulmonary hypertension: A retrospective analysis

[version 1; peer review: 1 not approved]
PUBLISHED 08 Jul 2024
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Abstract

Background

Cardiac amyloidosis, characterized by the deposition of amyloid proteins in the heart tissue, presents in two main types: transthyretin (ATTR) and light-chain (AL) amyloidosis. The hemodynamic response to exercise and the relationship with pulmonary hypertension (PH) in these patients is not well understood.

Methods

This retrospective study analyzed 100 patients diagnosed with either ATTR or AL amyloidosis. We assessed the prevalence of PH at rest and its induction during exercise stress tests. Hemodynamic parameters were measured to identify differences in the cardiac response to exercise between the two subtypes.

Results

A higher prevalence of PH was noted in the ATTR group compared to the AL group. Exercise stress tests induced significant PH, particularly in the ATTR subgroup. Subtle yet clinically relevant hemodynamic differences were observed between the amyloidosis subtypes.

Conclusions

Our findings suggest that the amyloidosis subtype is an important factor in the management of PH. There is a need for tailored clinical approaches to address the distinct pathophysiological mechanisms in ATTR and AL amyloidosis. This study contributes to a better understanding of the hemodynamic changes during exercise in cardiac amyloidosis and underscores the importance of subtype-specific management strategies.

Keywords

Cardiac Amyloidosis, Chronic Heart Failure, Exercise-Induced PH, Hemodynamic Response

Introduction

Cardiac amyloidosis, typified by ATTR (transthyretin) and AL (light-chain) amyloidosis, represents a spectrum of conditions characterized by extracellular deposition of misfolded proteins in the cardiac matrix, leading to diastolic dysfunction and restrictive cardiomyopathy.1,2 The intricacies of cardiac amyloidosis, coupled with its clinical manifestations, present a diagnostic challenge, often leading to delayed or missed diagnoses.3

Recent research underscores the prevalence of pulmonary hypertension (PH) in patients with cardiac amyloidosis, revealing its potential impact on prognosis and management strategies.4 ATTR amyloidosis, a hereditary or wild-type form, and AL amyloidosis, associated with plasma cell dyscrasia, each have distinct pathophysiological profiles but share the common complication of PH, contributing to increased morbidity and mortality.5

The hemodynamic burden imposed by amyloid deposition in the myocardium is not fully understood, especially under conditions of stress or exercise.6 This study aims to elucidate the hemodynamic changes associated with ATTR and AL amyloidosis at rest and during exercise, examining the prevalence of PH and its induction through stress testing to better understand the physiological demands placed on the heart in the presence of amyloid fibril infiltration.

By exploring the interplay between ATTR and AL amyloidosis with exercise-induced PH, this study aims to provide deeper insights into the hemodynamic alterations and their clinical implications, thereby informing more targeted therapeutic approaches for this patient population.

Methods

This retrospective cohort study analyzes the hemodynamic data from ATTR and AL amyloidosis patients between January 2015 and December 2023. Our primary aim was to compare the prevalence and severity of pulmonary hypertension (PH) and exercise-induced hemodynamic changes between the two amyloidosis types.

Study population

100 patients diagnosed with cardiac amyloidosis, confirmed via biopsy, were included. Of these, 40 had ATTR amyloidosis and 60 had AL amyloidosis.

Hemodynamic assessment

All patients underwent right heart catheterization (RHC) at rest. A subset of 70 patients also participated in exercise tests to induce PH. Hemodynamic parameters including mean pulmonary artery pressure (mPAP), pulmonary capillary wedge pressure (PCWP), and right atrial pressure (RAP) were recorded. The change in mPAP relative to cardiac output (ΔmPAP/ΔCO) was used to assess the exercise-induced PH. Exercise-induced pulmonary hypertension (PH) is characterized by an increase in mean pulmonary arterial pressure (mPAP) to >30 mmHg at a cardiac output (CO) of <10 L/min during exercise, or a total pulmonary vascular resistance (TPVR) >3 Wood units (WU). Additionally, a rise in mean pulmonary arterial pressure relative to the increase in cardiac output (ΔmPAP/ΔCO) exceeding 3 mmHg/L/min, and an elevation in pulmonary arterial wedge pressure (ΔPAWP/ΔCO) surpassing 2 mmHg/L/min from rest to exercise, indicate post-capillary exercise-induced PH.7

Statistical analysis

Differences in PH prevalence between ATTR and AL groups were compared using the chi-square test, and exercise-induced hemodynamic changes were analyzed with the Mann-Whitney U test. A p-value of less than 0.05 was considered statistically significant.

Ethical considerations

This study was approved by IRB at UNMC, Ethical Approval Committee: 0839-21-CB (12/2/2021). Due to the retrospective nature of the data analysis, the requirement for informed consent was waived. The study adhered to the ethical principles outlined in the Declaration of Helsinki for medical research involving human subjects.

Results

Our study's cohort featured 100 patients with cardiac amyloidosis, 40 with transthyretin amyloidosis (ATTR), and 60 with light-chain amyloidosis (AL) otherwise no difference in demographics Table 1. The incidence of pulmonary hypertension (PH) was higher in the ATTR group at 66% compared to 57% in the AL group, a difference that was on the cusp of statistical significance (p=0.051) Figure 1.

Table 1. Clinical Parameters of the Study Cohort.

ParameterATTRAL (n=60)
Age (years)65 ± 1062 ± 11
Gender male {%)60%55%
Body mass index (kg/m2)28 ± 427 ± 5
Systolic blood pressure (mmHg)130 ± 15125 ± 20
Diastolic blood pressure (mmHg)80 ± 1078 ± 12
NYHA functional class ≥3 {%)40%35%
N-terminal pro B-type natriuretic peptide (ng/L)3000 ± 5002800 ± 600
Troponin T (ng/L)0.05 ± 0.010.04 ± 0.02
Creatinine (μmol/L)110 ± 20100 ± 25
Estimated glomerular filtration rate (ml/min/1.73 m2)55 ± 1060 ± 15
Hereditary ATTR-CM {%)30%-
Hypertension {%)50%55%
Diabetes mellitus {%)20%25%
Previous stroke or TIA {%)10%8%
Chronic obstructive pulmonary disease {%)15%10%
Atrial fibrillation {%)25%20%
Carpal tunnel syndrome {%)35%30%
Spinal stenosis {%)5%8%
Left ventricular ejection fraction {%)50 ± 548 ± 6
lnterventricular septum diastolic diameter (mm)12 ± 211 ± 3
Left atrial area (cm2)20 ± 422 ± 5
2916230f-c904-4529-9e3d-684282e6ebd6_figure1.gif

Figure 1. Prevalence of Pulmonary Hypertension in ATTR vs. AL Amyloidosis.

Upon exercise stress testing, PH was elicited in the entirety of the ATTR subgroup and 90% of the AL subgroup, marking a significant differential response to physical exertion (p=0.04). Detailed hemodynamic profiling during exercise unveiled a nuanced interplay between ventricular response and vascular load. The median increase in mean pulmonary arterial pressure relative to cardiac output (ΔmPAP/ΔCO) was marginally higher for ATTR patients. Similarly, the median rise in pulmonary artery wedge pressure per unit cardiac output (ΔPAWP/ΔCO) also favored ATTR amyloidosis, though this did not reach a level of statistical significance Figure 2.

2916230f-c904-4529-9e3d-684282e6ebd6_figure2.gif

Figure 2. Hemodynamic Changes During Exercise.

Notably, the median increase in right atrial pressure per unit cardiac output (ΔRAP/ΔCO) was marginally higher in the AL group, reflecting a potential difference in central venous pressure dynamics during stress between the amyloidosis types. Nonetheless, the ratio of ΔRAP to ΔPAWP remained consistent across both groups, suggesting a uniform relationship between right atrial pressures and left-sided filling pressures during exercise, regardless of amyloid type (p=0.08) Table 2.

Table 2. Hemodynamic Variables at Rest and During Exercise.

Hemodynamic VariableRest ATTRExercise ATTRRest ALExcercise AL
Heart Rate (b.p.m)70 ± 1285 ± 1572 ± 1188 ± 14
Arterial 02 saturation (%)95 ± 396 ± 294 ± 495 ± 3
Cardiac output (L/min)4.6 ± 1.16.5 ± 1.24.4 ± 1.06.2 ± 1.3
Stroke volume (ml)65 ± 1575 ± 1863 ± 1473 ± 17
Right atrial pressure (mmHg)8 [S-12]10 [7-14]7 [4-11]9 [6-13]
Systolic pulmonary artery pressure (mmHg)35 ± 1040 ± 1233 ± 1138 ± 13
Diastolic pulmonary artery pressure (mmHg)15 ± 520 ± 614 ± 618 ± 7
Mean pulmonary artery pressure (mmHg)25 ± 830 ± 1024 ± 928 ± 11
Pulmonary capillary wedge pressure (mmHg)12 [8-16]15 [10-20]11 [7-15]14 [9-19]
Pulmonary vascular resistance (Wood units)1.5 [1.2-2.0]1.3 [1.0-1.7]1.6 [1.3-2.1]1.4 [1.1-1.8]
Pulmonary arterial compliance (mL/mmHg)3.0 [2.5-3.S]2.8 [2.3-3.2]3.1 [2.6-3.7]2.9 [2.4-3.4]

These findings illuminate the pathophysiological divergence in exercise response between ATTR and AL amyloidosis, underscoring the need for tailored clinical management strategies.

Discussion

This study's findings reveal a complex interplay between cardiac amyloidosis subtypes and pulmonary hypertension (PH), particularly under exercise conditions.8 The higher prevalence of exercise-induced PH in ATTR compared to AL amyloidosis may reflect the distinct pathophysiological mechanisms at play.9 ATTR amyloidosis, with its non-mutant and mutant variants, often leads to stiffer ventricular walls, predisposing patients to a higher incidence of PH during stress.7

The marginal differences in hemodynamic responses, such as ΔmPAP/ΔCO and ΔPAWP/ΔCO, suggest a possible disparity in how each amyloid subtype affects cardiac and vascular function.10 These disparities could be attributed to the differential myocardial infiltration patterns and the resultant impact on ventricular compliance and contractility. The similar ΔRAP/ΔPAWP ratios between the groups might indicate a shared mechanism in the way increased left heart pressures are transmitted back to the right heart, despite the differences in amyloid fibril composition anetd deposition.

The borderline statistical significance observed in PH prevalence and hemodynamic responses warrants further investigation. A larger sample size could elucidate whether the trends observed are consistent and statistically robust across a broader population.

Clinically, these findings emphasize the importance of personalized management strategies for PH in patients with cardiac amyloidosis.4 They also raise questions about the potential benefits of targeted therapies for PH that consider the specific amyloidosis subtype. Prospective studies might investigate whether treatments that are effective for PH in one subtype may be less so in another, due to the underlying molecular and structural differences.

This research contributes to a growing body of evidence that suggests cardiac amyloidosis, particularly ATTR, is an underrecognized etiology in patients presenting with PH.10 Recognition of this relationship is critical, as it may guide the timing of diagnostic procedures like RHC, especially when noninvasive assessments are inconclusive or suggest PH. It also underscores the need for heightened clinical awareness of amyloidosis as a differential diagnosis in PH patients.

Conclusion

The hemodynamic response to exercise in cardiac amyloidosis patients with PH presents a multifaceted challenge. Our study adds to the understanding of this response, providing a foundation for future research and clinical practice that could improve outcomes for this patient population.

Ethical approval committee

0839-21-CB (12/2/2021).

Author contributions statement

Authors AA & KS were involved in the conception and design, and author HA was involved in the analysis and interpretation of the data; the drafting of the paper, revising it critically for intellectual content; and the final approval of the version to be published. All authors agree to be accountable for all aspects of the work.

Ethics and consent

This study was approved by IRB at UNMC, Ethical Approval Committee: 0839-21-CB (12/2/2021). Due to the retrospective nature of the data analysis, the requirement for informed consent was waived. The study adhered to the ethical principles outlined in the Declaration of Helsinki for medical research involving human subjects.

Description of data restrictions

Our study involves data that are sensitive in nature due to [patient confidentiality, proprietary information]. To protect the privacy and rights of the individuals involved and to comply with [local institute regulations and guidelines], access to the complete dataset is restricted.

Information required for data access application

Researchers or reviewers interested in accessing the dataset must:

  • 1. Submit a formal request to [specify the authority, e.g., the principal investigator, a specific department, or an institutional review board] outlining the purpose of the data request.

  • 2. Provide a detailed research proposal, including objectives, methodology, and expected outcomes.

  • 3. Agree to abide by all ethical guidelines, including [specify any specific requirements, such as data handling procedures, confidentiality agreements, etc.].

  • 4. Obtain approval from their own institutional review board (IRB) or ethics committee, if applicable.

Conditions for data access

Access to the data will be granted under the following conditions:

  • 1. The data will be used solely for the purposes outlined in the approved research proposal.

  • 2. Any publication or dissemination of results derived from the data must acknowledge the source of the data.

  • 3. The data must not be shared with third parties or used to identify individual participants.

  • 4. All researchers accessing the data agree to comply with [specify any additional conditions, such as data security measures, reporting requirements, etc.].

We believe these measures are necessary to ensure the ethical use of the data and to protect the privacy and security of the individuals and entities involved. Should you require any further information or clarification, please do not hesitate to contact us.

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how to cite this article
Albulushi A, Al-Busaidi A, Al-Lawatia K et al. Comparative hemodynamics of ATTR and AL amyloidosis with exercise-induced pulmonary hypertension: A retrospective analysis [version 1; peer review: 1 not approved]. F1000Research 2024, 13:769 (https://doi.org/10.12688/f1000research.148652.1)
NOTE: If applicable, it is important to ensure the information in square brackets after the title is included in all citations of this article.
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ApprovedThe paper is scientifically sound in its current form and only minor, if any, improvements are suggested
Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.
Not approvedFundamental flaws in the paper seriously undermine the findings and conclusions
Version 1
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Reviewer Report 04 Sep 2024
Selda Murat, Eskisehir Osmangazi University, Eskisehir, Turkey 
Not Approved
VIEWS 4
The methodology of the study is not suitable for retrospective data recording studies.
It should be explained for which indications right catheter and exercise-induced catheter were performed after diagnosis.

If these interventional procedures were performed within ... Continue reading
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Murat S. Reviewer Report For: Comparative hemodynamics of ATTR and AL amyloidosis with exercise-induced pulmonary hypertension: A retrospective analysis [version 1; peer review: 1 not approved]. F1000Research 2024, 13:769 (https://doi.org/10.5256/f1000research.162992.r314999)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.
  • Author Response 05 Sep 2024
    SS DM2020, Division of Adult Cardiology, National Heart Center, The Royal Hospital, Muscat, Oman
    05 Sep 2024
    Author Response
    1. Methodology of the study is not suitable for retrospective data recording studies.
    Response:
    Thank you for pointing this out. We recognize that the retrospective nature of our study may ... Continue reading
COMMENTS ON THIS REPORT
  • Author Response 05 Sep 2024
    SS DM2020, Division of Adult Cardiology, National Heart Center, The Royal Hospital, Muscat, Oman
    05 Sep 2024
    Author Response
    1. Methodology of the study is not suitable for retrospective data recording studies.
    Response:
    Thank you for pointing this out. We recognize that the retrospective nature of our study may ... Continue reading

Comments on this article Comments (0)

Version 1
VERSION 1 PUBLISHED 08 Jul 2024
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Alongside their report, reviewers assign a status to the article:
Approved - the paper is scientifically sound in its current form and only minor, if any, improvements are suggested
Approved with reservations - A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.
Not approved - fundamental flaws in the paper seriously undermine the findings and conclusions
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