A rare cause of dyspnea on exertion with a cardiopulmonary exercise stress test

Informative abstract

Background

It is rare for an adult patient to be living decades after a pneumonectomy procedure. This case features complications that can arise. We utilize cardiopulmonary exercise stress testing (CPET) to highlight long-term physiologic changes that can present in a post-pneumonectomy patient.

Case presentation

A 53-year-old woman presented for cardiopulmonary exercise stress testing (CPET) to assess worsening dyspnea on exertion with associated chest pressure. She had a history of traumatic right-sided pneumonectomy at age 27 years complicated by post-pneumonectomy syndrome. Her CPET was suboptimal with marked deficiencies that were most consistent with a primary ventilation limitation causing her reduced exercise capacity.

Discussion/conclusion

A thorough literature search did not return any similar cases using CPET to evaluate a post-pneumonectomy patient. The abnormal anatomy results in a unique set of CPET values. Her ventilatory insufficiency is likely made worse by her post-pneumonectomy syndrome. Her treatment options are limited.

Descriptive abstract:It is rare for an adult patient to be living decades after a pneumonectomy procedure. This case report features complications in a 53-year-old female who is 26 years post-pneumonectomy and presented to cardiology clinic with worsening dyspnea on exertion. Cardiopulmonary stress testing (CPET) was used to rule out cardiac pathology. The patient's unusual CPET results highlight long-term physiologic changes that can present in a post-pneumonectomy patient. The abnormal anatomy results in a unique set of CPET values that were not previously well defined in the existing literature.

1. Case description

A 53-year-old female presented to the cardiology outpatient clinic to evaluate worsening dyspnea on exertion. She complained of associated substernal chest pressure raising concern for myocardial ischemia. Clinical history revealed a prior penetrating gunshot wound to the right thorax at age 27 years for which she had undergone emergent right pneumonectomy. She had a late complication of post-pneumonectomy syndrome 7 years after surgery that presented with symptoms of dyspnea from compression of the left mainstem bronchus. The patient underwent mediastinal repositioning surgery with placement of saline implants into the postpneumonectomy space, however she had a cardiac arrest during the procedure that necessitated removal of the implants and termination of surgery. Three years later, a Dumon stent was placed in the left mainstem bronchus with little symptomatic improvement.

Despite a complicated history, the patient attempted to maintain average physical activity levels. However, she reported gradually worsening shortness of breath with exertion over the years. By the time of presentation, she had begun to use 2L supplemental oxygen for comfort during exertional activities.

A posterior-anterior chest radiograph (Fig. 1) showed complete opacification of the right hemithorax with mediastinal and tracheal shift to the right The left lung appeared well expanded. No pulmonary edema or lesion was present in the left lung. A CT chest angiogram was negative for acute pulmonary embolus. The CT images also demonstrated rightward mediastinal shift. The left pulmonary artery was anatomically kinked measuring 15mm in the smallest dimension but was without evidence of significant luminal narrowing (Fig. 2). The trachea and left main stem bronchus were not significantly narrowed.

Fig. 1.

Anterior-posterior plain film showing absence of the right lung and shifted mediastinum.

Fig. 2.

Coronal CT image showing slight kinking (red arrow) of the pulmonary artery without evidence of significant narrowing. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Pulmonary function testing (PFTs) showed severely reduced FEV1 1.03L (37% predicted) and FVC 1.51L (43% predicted). The FEV1/FVC ratio suggested an obstructive pattern. The DLCO was 64% predicted, indicative of a limited diffusing capacity. The TLC was 3.01L (59% predicted), VC 1.42L (40% predicted), and FRCpleth 1.68L (61% predicted).

The patient underwent Mayo Treadmill Protocol Cardiopulmonary Exercise Testing (CPET) (see Table 1)and completed 4.8 minutes of exercise equal to 54% predicted for age and gender. Peak METS achieved was 5.1. The test was terminated due to severe dyspnea and lightheadedness. Peak heart rate during the test was 135 beats per minute, 81% of predicted, with no significant arrhythmias. Blood pressure increased appropriately from 132/80mmHg- 204/72mmHg. The ECG throughout exercise was negative for ischemia.

Table 1.

Cardiopulmonary exercise test results without supplemental O2.

	Test result	Predicted	% Predicted	Classification
Exercise time (min)	4.8	9	54 %	Limited
Resting heart rate (bpm)	90	–	–	–
Peak heart rate (bpm)	136	168	81 %	Limited heart rate response
Peak systolic pressure (mmHg)	204	130–224	–	Normal blood pressure response
Peak RER	0.92	>1.10	–	Submaximal cardiometabolic effort
Peak VO2 (mL/kg/min)	18.0	25.7	70 %	Limited
Peak ventilation (L/min)	42	42	100 %	0 % breathing reserve
Resting SpO2	98 %	>/ = 90 %	–	Normal
Minimum SpO2	93 %	>/ = 90 %	–	Mild decrease in saturation during the limited duration of exercise
VE/VCO2 slope	24	20.7–32.6	–	Normal

In terms of gas exchange, peak respiratory exchange ratio (RER) during the test was 0.92, demonstrating less than maximal effort from a cardiometabolic standpoint. Peak VO2 was 18.0 mL/kg/min consistent with limited capacity (70% of expected) but VE/VCO2 was normal reflecting normal gas exchange function of pulmonary vasculature. Peak ventilation was 42 L/min, exactly 100% of predicted by the FEV1 with 0% breathing reserve at peak exercise. Vd/Vt decreased at the onset of exercise as expected but then flattened.

Pre-exercise SpO2 was 98%. SpO2 without supplemental oxygen dropped to 93% during exercise. CPET was repeated later with the addition of 2L supplemental oxygen via nasal cannula. SpO2 improved to 95% during exercise, but overall performance was unchanged from the first test.

2. Discussion

Cardiopulmonary exercise testing (CPET) is used to assess the interaction between pulmonary function, cardiovascular status, and oxygen uptake in the skeletal muscle system [1]. CPET can help determine the cause of exercise intolerance in patients. It has been used consistently to evaluate patients prior to lung resection as a means to predict outcomes [2]. However, there are virtually no case reports of postoperative CPET to evaluate patients after pneumonectomies, particularly those with post-pneumonectomy syndrome.

The patient's CPET was not expected to be normal with a single functioning lung. Post-pneumonectomy, the forced vital capacity (FVC) and total lung capacity (TLC) decrease to approximately 60–65% of pre-surgical volume [3]. The alveolar-capillary surface area is reduced to a single lung, and the entire cardiac output must continue to circulate through that available area. Thus, the pulmonary capillary blood volume is increased, and the diffusing capacity of carbon monoxide (DLCO) decreases proportionally [3]. The maximum VO2 is not expected to drop as much as the FVC or DLCO [3,4]. Cardiac output and stroke volume will decrease proportionally with VO2 [3,4].

In our patient, CPET was submaximal from a cardiometabolic standpoint with normal cardiac responses to level tested. The test was terminated for severe dyspnea with a breathing reserve of 0%. Ventilatory equivalent for CO2 was normal but mild desaturation was noted. VE/VCO2 was normal reflecting normal function of pulmonary vasculature. Early flattening of Vd/Vt suggests diminished breathing mechanics. Exercise was clearly ventilation limited.

Several features of this case make it unique. Traumatic pneumonectomies are uncommon and carry greater than 50% mortality rate [5]. The most likely indication for total pneumonectomy is lung cancer, and most of those surgical patients do not have protracted life expectancies. It is unusual for a pneumonectomy patient to be living almost 30 years post-procedure. Furthermore, post-pneumonectomy syndrome is a rare sequela of pneumonectomy that is mostly seen in children [6]. It is characterized by mediastinal shift that compresses the airway between the pulmonary artery and aorta or vertebral column [6]. Symptoms can be managed with saline implants into the post-pneumonectomy cavity and/or bronchial stents, both of which this patient had attempted.

Unfortunately, future management options for this patient are limited. Consideration was given to sling surgery to improve pulmonary arterial flow, however CPET results did not support a restricted cardiac output, thus the procedure was deferred. The CPET limitation was clearly pulmonary, not vascular, and improving pulmonary arterial blood flow would not reasonably improve exercise limitation. Moreover, a ventilation-perfusion scan showed adequate perfusion to the left lung despite the anatomical kinking. A lung transplant was considered but would not be feasible into the scarred post-pneumonectomy space in the right thorax, nor would a transplant be indicated for the left lung that displays normal parenchymal activity. Though supplemental oxygen had a clinically insignificant impact on SpO2 concentration and no effect on peak ventilation during exercise, the patient chooses to continue using 2L oxygen for comfort during exertional activities.

Funding

Not applicable.

Ethical approval

Not applicable.

Guarantor

Not applicable.

Contributorship

Not applicable.

CRediT authorship contribution statement

Elizabeth H. Lees: Writing – review & editing, Writing – original draft. Hernan Cardozo Torres: Writing – review & editing. Eric S. Edell: Writing – review & editing, Data curation. Gustavo Cortes Puentes: Writing – review & editing, Conceptualization. Thomas A. Foley: Writing – review & editing, Investigation. Janani S. Reisenauer: Writing – review & editing, Investigation. Thomas G. Allison: Writing – review & editing, Writing – original draft, Supervision, Conceptualization.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Handling Editor: DR AC Amit Chopra