Isolated Pulmonary Valve Endocarditis with Rapid Progress: a Case Report and Literatures Reivew

Background: Isolated pulmonary valve endocarditis (IPE) is rare, accounting for 1.5-2% of all cases of infective endocarditis. Herein, we describe a case of isolated pulmonary valve endocarditis in a 28-year-old male with rapid progress. Unlike most patients reported before who were cured only by anti-infective therapy, without surgery at early stage, multiple complications occured in this patient in less than 2 weeks. Case presentation: The patient was diagnosed as pulmonary valve endocarditis with blood cultures showing Staphylococcus aureus and echocardiogram revealing 2 masses (measured 14*13mm (cid:0) 11*16mm respectively). Only 12 days later, acute massive pulmonary embolism occured. Then repeated echocardiogram revealed multiple massed attached to pulmonary valve with severe pulmonary insuciency and possibility of pulmonary valve destruction. Finally, pulmonary valve replacement, vegetation removal, right pulmonary thromboendarterectomy together with resection of the middle and lower lobes of the right lung were performed. Conclusions:The role of surgery at early stage might need reconsideration, it may be viable to combine medical and surgical approaches.


Background
Isolated pulmonary valve endocarditis (IPE) represents 1.5-2% of all cases of infective endocarditis [1] (IE). Intravenous drug abuse, sepsis, central venous catheter or pacemaker implantation account for the majority of risk factors [2] . Most data about pulmonary valve(PV) infective endocarditis is mainly reported in small case series and case reports, some of which were published 25 years ago. Herein, we describe a case of IPE in a 28-year-old male complicated with rapid progress and multiple pulmonary emboli. Unlike most patients reported before who were cured only by anti-infective therapy, multiple complications occured in this patient in less than 2 weeks.

Case Presentation
A 28-year-old male was referred to the emergency department coupled with fever and chills for 2 weeks and was diagnosed as infective endocarditis in other hospital. He reported that he had a two-week travel in deserts of United States and accidentally broke the left ankle skin 2 weeks ago. There was no history of diabetes or hypertension and no family history.Then he presented to a hospital in US and was treated with ibuprofen for high fever (value unknown), however, his body temperature normalized for few hours then rose again with decreased appetite. With a body temperature of 40.3℃, he was admitted to a hospital in Beijing 10 days ago. Investigations revealed a white blood cell (WBC) count of 14.30*10 9 /L, urine WBC count 106.8/ul, urine red blood cell count 34.9/ul, urine culture bacterium count 203.2/ul, and repeated blood cultures showed Staphylococcus aureus. Chest CT(computed tomography) showed multiple in ammatory changes in both lungs, so the patient started on anti-infective therapy by ceftriaxone and clarithromycin. During the treatment, fever repeated and his body temperature ranged from 38.6 to 40.3℃ with cough and white phlegm. An echocardiogram revealed 2 masses ( measured 14*13mm 11*16 mm respectively), which were very mobile and appeared to be attached to the pulmonary valve. Then the patient was referred to our hospital with WBC count of 16.4 × 10 9 /L, CRP(Creactive protein) 113.2 mg/L, and echocardiogram (just one day later than the previous one) showed a mass attached to the pulmonary valve, which is measured 43.8*19.9 mm. The chest radiology revealed that multiple patchy and large lesions with cavities in both lungs. So the patient was diagnosed as endocarditis, septicemia and pulmonary infection, and was admitted to our hospital.
Given the patient age and short antibiotic treatment duration, valve replacement surgery is not the priority option and the patient wanted to reconsider the surgery, so the treatment was mainly anti-infective and supportive therapy. Two days later, the patient reported chest tightness, dyspnea with increased DDi(D-Dimer)(5.60 µg/mL) after using the toilet, and CTPA(computed tomographic pulmonary angiography) revealed lling defect of the right pulmonary artery and its branches, and some branches of the left pulmonary artery, which was considered to be pulmonary embolism. Therefore, the patient was transferred to ICU(intensive care unit) and immediately conducted the interventional pulmonary artery thrombectomy. After a-week treatment in ICU, the patient was transferred to cardiac surgery department to prepare for valve replacement surgery, as the last echocardiogram showed multiple massed attached to pulmonary valve with severe pulmonary insu ciency and possibility of pulmonary valve destruction( Fig. 1). Nevertheless, repeated blood culture was negative. Latest CTPA and chest CT showed right lower pulmonary embolism and right lower lobe pneumonia (Fig. 2). Twenty days later, given the poor effect of anti-infective treatment and the strong operation desire of patient, pulmonary valve replacement, vegetation removal and right pulmonary thromboendarterectomy were performed. Destroyed pulmonary valve lea ets with friable vegetation measured 2.5*1.0 cm and gray vegetation in right pulmonary artery were revealed (Fig. 3). Radical debridement with valve excision was performed, and then 23#StJude bioprosthetic valve was interrupted sutured. Under direct vision through an incision into the right pulmonary artery, thrombus was removed with double-lumen catheter. During the operation, bronchoscopy showed that blood lled all levels of the bronchus at both sides, and active hemorrhage in distal right middle bronchus. After brief multidisciplinary discussion, resection of the middle and lower lobes of the right lung was conducted.
Histopathology revealed infectious destruction in the specimen from the pulmonary valve and extensive hemorrhage and infarction of lung tissue with in ammatory cells in ltration. The patient's postoperative course was uneventful and laboratory parameters were all normalized before his discharge. He was discharged on the 30th postoperative day. The patient continued antibiotic therapy for a month after operation. Mean peak systolic transvalvular gradients were 19 mmHg, 24 mmHg and 23 mmHg on postoperative day 8, day 23 and day 85 by echocardiography.

Discussion And Conclusion
Right-sided IE, especially IPE is rare, occurring ten times less frequently than tricuspid valve endocarditis [1] . A structurally normal pulmonary valve is hardly affected alone. The rst possible reason is that the lower pressure gradient through the pulmonary valve results in less shear stress than other valves. This leads to less valvular damage and protects PV from IE occurrence. Secondly, valvular abnormalities are rare in PV.
In a prospective cohort study, the main pathogenic microorganism isolated from blood culture was gram's bacteria (83%), of which Staphylococcus aureus accounted for 31% [3] . And the most common pathogenic microorganism in north America is Staphylococcus aureus [3] , which is consistent with the patient's history and blood culture.
In the review of our patient, a rapidly progressive course was observed. The patient was diagnosed as bacteremia 4 days after his rst fever and went on antibiotic therapy. The blood culture result came out on the 7th day and antibiotics were adjusted according to it. On the 12th day, vegetations were discovered and measured 14*13 mm,11*16 mm, while one day later, the whole vegetation measurement was 43.8*19.9 mm. Then the patient was transferred to ICU for pulmonary embolism on the 16th day. Most embolism events occurred in 2-4 week of antibiotic therapy [4] . While in this case, pulmonary embolism occurred in less than 2 weeks. Furthermore, except for the rst blood culture, the repeated ones later stayed negative as situation deteriorated rapidly, which makes the treatment more complicated.
It seems that surgery is not the optimal treatment for right-sided IE. AHA(American Heart Association) guidelines [5] recommended that right-sided IE should be treated as conservatively as possible, and nonrandomized trial data from single center experience [6] and international collaboration [7] support that early valve surgery may not be bene cial to all primary patients caused by Staphylococcus aureus. And even the ESC(European Society of Cardiology) guidelines do not explain the role of surgery in pulmonary valve infection [8] . However, our patient indicated embolization, valve destruction, and large vegetation, and general situation deteriorated in a short time. The role of surgery at early stage in patients with such rapid course and multiple complications, might need reconsideration.
As AHA guidelines [5] recommended, both TTE(transthoracic echocardiography) and TEE(transesophageal echocardiography) are indispensable in many patients with IE during initial evaluation and subsequent follow-up and provide complementary information. It is estimated that the sensitivity and speci city of TTE is 30-63% and 91-100%, and those of TEE is 87-100% and 91-100% [9] . Even if our patient's blood culture stayed negative, TTE provided extra information to evaluate severity of IE. Robbins et al. found that vegetation size can predict the response to medication alone [10] . The response to medication of vegetations < 10 mm is 100% verse 63% in those > 10 mm, and surgery is unavoidable for the rest. In their assumption, as bacterial colonies deepen, their metabolism and proliferation get slower, leading to certain antibiotics less effective. All these evidences indicate that our patient might bene t more from surgery than conservative treatment alone.
A prospective cohort study, early surgery is found to be essential to improve the survival rate of patients with IE.Postoperative results are generally favorable, as two of the largest case series reporting that none of the nine cases had repeated vegetation [11] [12] . The bioprosthetic valve of our patient functioned well and stably after 3 months' follow-up. However, optimal surgical strategy for IPE has not been fully investigated. As some reports supporting early surgical interventions, it may be viable to combine medical and surgical approaches in IE patients on admission.

Declarations
Ethics approval and consent to participate Written informed consent was obtained from the patient.

Consent for publication
Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor of this journal.

Availability of data and materials
Authors do not wish to share the data because that it might identify the patient.

Competing interests
The authors declare that they have no competing interests Authors' contributions ZMX reviewed the literature and contributed to manuscript drafting; WB and ZBW were responsible for the revision of the manuscript for important intellectual content and reviewed the literature; YC and WB were sonographers and collected data, reviewed the literature; ZWM was the patient's surgeon, who provided records of patients, and contributed to the manuscript drafting; CR and PM reviewed the literature. All authors issued nal approval for the version to be submitted.

Figure 1
A series of ultrasonography showing PV vegetation from one day before admission to 2 days before operation. Multiple vegetations were observed and one of them were measured in b-g. a was performed one day before admission, b and c were on day 1 after admission. And d, e, f, g was on day 8, 12, 16, 26 respectively.