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- Exercise as it relates to Disease
This is a critical analysis on the article from the Journal of the American College of Cardiology “Pulmonary Hypertension and Exercise Intolerance in Patients with Heart Failure” – Javed Butler, MD; Don B Chomsky (1999).[1]
Major signs and symptoms of heart failure: Authors: National Heart, Lung and Blood Institute; National Institute of Health (Image: National Heart, Lung, and Blood Institute , National Institutes of Health ; orig, Public domain)
What is the background to this research?
Exercise is the archetype of physiological demands placed on the body. It greatly benefits patients, though the capacity to exercise is frequently reduced in those with heart failure1]. [Heart failure occurs when the heart cannot keep up with the bodies workload, caused by impaired systole and diastole performance. The heart takes temporary measures to try mask the problem including:
- Stretching (enlargement)
- Increased heart-rate
- Vasoconstriction (compensation for power loss)[2]
Exercise intolerance is a serious problem in heart failure patients; characterised by fatigue, shortness of breath and sometimes coughing. Pulmonary vascular resistance (PVR) may contribute to this exercise intolerance by impaired pulmonary blood flow1]. During exercise, pulmonary pressure increases due to increased blood flow. [Cardiac output then increases due to pulmonary pressures, resulting in a drop in PVR[2][3].
Regardless of the etiology of heart failure, exercise has modest clinical benefits. Though exercise is dangerous when these complications aren’t taken into consideration.
Where is the research from?
The article was published in the Journal of the American College of Cardiology by Elsevier Science Inc. Per Impact Factor, it was deemed the top Cardiovascular Journal worldwide (2013–2016). The funding was a Grant-in-Aid from the National American Heart Association. There is no evidence of bias regarding the large voluntary non-for-profit organisation, labelled ‘trustworthy’ in compliance with HONcode (Health On the Net Foundation). The study was approved by the National Institutes of Health.
Primary author, Javed Butler, has a strong cardiovascular repute, being board certified in cardiovascular/ transplant medicine, and advanced heart failure. He has written 450+ peer-reviewed publications, and is on the editorial board of several cardiovascular journals. Dr. Don B Chomsky, has 27 years of experience in specialty fields of cardiovascular disease and internal medicine.
What kind of research was this?
This is an observational cross-sectional study; involving a snapshot of the clinical population at a set point. The data derived can contain multiple variables, though won’t help determine cause/ effect. The population are not compared to a control group, instead compared within each other. It would make it easier to decipher clinical results if derived from normal population findings.
What did the research involve?
The research for this study involved 320 ambulatory patients, who underwent cardiac catheterisation at the Vanderbilt Heart Failure and Transplant Programs, between December 1993 - March 1997. The criteria included:
- An ejection fraction of <40%
- No inotrope dependancy/ mechanical support
- No exercise angina limitations
- No arterial oxygen desaturation/ hypoxemia exhibitation
The protocol initially involved a cardiac catheterisation insertion procedure. Supine central hemodynamic measurements were monitored (at rest and throughout exercise); including blood pressure, haemoglobin oxygen saturation, pulmonary arterial pressure, right atrial pressure and pulmonary wedge pressure. Participants performed a modified Naughton Protocol on a treadmill (3 minute stages) to find peak VO2. Patients continued exercising until symptoms of dyspnea/ fatigue forced them to stop. Respiratory gas exchange analysis and blood sampling was also taken.
| Severity Group | Resting Pulmonary Hypertension (Wood Units) | % of patients |
|---|---|---|
| 1 - Normal | <1.5 | 28% |
| 2 - Mildly Elevated | 1.5 - 2.49 | 36% |
| 3 - Moderately Elevated | 2.5 - 3.49 | 17% |
| 4 - Severely Elevated | >3.5 | 19% |
This methodology was not the best approach. The patient population holds bias, as patients with mild heart failure are rarely referred to specialty heart failure/ transplant programs1]. Perhaps having a wider patient cohort and/or a control group could allow for a greater comparison. The time frame this study was conducted in seems unreasonable, due to [cardiac catheterisation being a lengthy process. Not to mention the ~$1.365 million (at ~$4265.21 per patient) cost[4]. Pushing participants to exhaustion could be dangerous regardless of meeting exclusion criteria. No indication of incidences, further complications or care taken after the protocol for the patients were mentioned, which calls for question on supervision precautions taken. Also, no measure of client’s current medications/ history were stated.
What were the basic results?
| Baseline | Peak Exercise | |
|---|---|---|
| Pulmonary Wedge Pressure (mmHg) | 18 ± 0.9 | 23 ± 10 |
| Cardiac Output (L/min) | 4.5 ± 1.3 | 8.5 ± 3.0 |
| Pulmonary Vascular Resistance (Wood Units) | 2.45 ± 1.57 | 2.41 ± 1.52 |
| VO2 (ml/min/kg) | 13.0 ± 3.4 |
- 18% had peak VO2 of >16ml/min/kg
- Pulmonary wedge pressure decreased in 28% (indicating impairment of left ventricular filling)
- PVR increased in patients with normal resting pulmonary hypertension (Group 1)
- PVR decreased in patients with severe resting pulmonary hypertension (Group 4)
- The absence of major exertion symptoms does not exclude possibility of severe pulmonary hypertension
The implications of their findings were not over emphasised, as each statement follows statistical data. Most findings in this report display comparable results from similar studies (and are mentioned). However, some data throughout the study is inconsistent. It was stated in the results that 18% of the patients had peak VO2 levels >16ml/min/kg. In the discussion, it states the 16% of patients had the same result. Further on, it states 58/320 patients (18.1%) had >16ml/min/kg.
What conclusions can we take from this research?
The study concludes that the presence of pulmonary hypertension is not always associated with major exercise intolerance, and that it contributes by impairment of cardiac output response1]. The conclusion reinstates results, stating that the hypothesis was supported; though they do so in an unclear way. Initially it could be read that 50% of patients had a VO2 >16ml/min/kg, which is incorrect (stated as both 16% and 18% in the results/ discussion). Instead it states that from the 58 patients, half had [pulmonary hypertension, which is not clearly articulated throughout the study.
As the research was observed through a large cohort, there is a sufficient degree of evidence to support generalization. Although, the selection criteria is restricted as it only took patients from a specific transplant program. This bias in turn could damper results. Furthermore, there is no section for ‘study limitations/ suggestions for future research’ which could be beneficial for authors to reflect and suggest.
Practical advice
Vast progress in the diagnosis and treatment of heart failure has been confirmed over recent years. Due to this high prevalence, large amounts of research have been conducted to find the relationship between pulmonary hypertension and exercise performance. However, to compare with real-world implications, this study would be more applicable inclusive of diet (nutrition), patient medication, and physical activity levels being revealed.
It is vital that exercise be prescribed only after signing informed consent and completing an ESSA adult pre-exercise screening. This allows patient/ practitioner protection, through professional/ ethical conduct. Furthermore, strong supervision and precautions are fundamental for any exercise undertaken. This research was led by allied health professions with significant funding. In taking on this practical advice; understanding of considerations and guidelines are highly recommended.
Further information/ support
If you are interested in further reading about this subject matter; below are resources to provide additional information support:
- Heart Failure: Guidelines/ Tools: https://www.heartfoundation.org.au/for-professionals/clinical-information/heart-failure
- Effects of Hypertension: https://www.healthline.com/health/high-blood-pressure-hypertension/effect-on-body#1
- Catheter: Procedures/ Treatment: https://www.svhhearthealth.com.au/procedures/procedures-treatments/right-heart-catheter
- Catheterisation Animation: https://www.webmd.com/heart-disease/video/cardiac-catheterization
References
- ↑ a b c d e Butler, Javed ; Chomsky, Don B ; Wilson, John R; Pulmonary hypertension and exercise intolerance in patients with heart failure; Journal of the American College of Cardiology, 15 November 1999, Vol.34(6), pp.1802-1806
- ↑ a b American Heart Association. Heart Failure: What is heart failure? [Online].; 2018 cited 2018 September. Available from: [http://www.heart.org/en/health-topics/heart-failure/what-is-heart-failure
- ↑ Yen-Chun L, Karin P. Pulmonary Arterial Hypertension: The Clinical Syndrome. Circulation Research. 2014; 115(1): p. 115-130
- ↑ Sareen R. Costing of a cardiac catheterisation procedure. Academy of Journal Administration. 1997; 9(2): p. 31
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