Right lateral mini-thoracotomy approach for infective endocarditis in the aortic valve

Kayo Sugiyama^1*, Hirotaka Watanuki¹, Masato Tochii¹, Katsuhiko Matsuyama¹

¹Department of Cardiac Surgery, Aichi Medical University Hospital

      1 - 1  Yazako Karimata, Nagakute, Aichi, 480-1195, Japan

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Abstract

Purpose: To evaluate the clinical background and postoperative outcomes of patients with infective endocarditis in the aortic valve position and discuss the appropriate approach in the era of minimum invasive cardiac surgery.

Methods: We evaluated the preoperative background, intraoperative procedure, and postoperative outcomes of infective endocarditis in the aortic valve including 13 patients at our hospital. The right lateral mini-thoracotomy approach was introduced in six patients with localized infectious changes in the aortic valve.

Results: All surgical treatment were performed successfully, and there were no mortality or cardiac events related to recurrent infection. The right lateral mini-thoracotomy approach was completed safely; however, ventricular diverticulum was detected in multidetector computed tomography after surgery.

Conclusions: Infective endocarditis in the aortic valve was appropriately treated, and the postoperative course was favorable. The right lateral mini-thoracotomy approach is feasible, but it should be selected carefully only for cases with localized infection in the aortic valve.

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Introduction

Infective endocarditis (IE) localized at the aortic valve leaflet could be treated with simple aortic valve replacement. However, postoperative outcomes are poorer when IE is complicated by an aortic root abscess compared to cases confined to the aortic valve^1,2. In such cases, aortic root repair or reconstruction may be necessary after abscess debridement. Ensuring a clear surgical field is crucial for effective removal of infected tissue.

Recently, the use of minimum invasive cardiac surgery (MICS) has increased rapidly^3-5 to reduce postoperative complications associated with median sternotomy. The rationale for MICS extends beyond cosmetic benefits; it also minimizes surgical trauma, reduces complication rates and blood loss, and shortens recovery time ^6-11.

In Japan, the right lateral mini-thoracotomy approach is widely used more than mini-sternotomy or right anterior thoracotomy. We have adopted this approach for aortic valve surgery, in addition to its established use in mitral valve procedures (Fig. 1a). However, the application of MICS for IE requires careful consideration. The American Association for Thoracic Surgery guidelines recommend median sternotomy for most IE surgeries due to the high likelihood of unexpected findings or more advanced disease than initially anticipated¹². The guidelines also emphasize the need for good exposure to ensure thorough debridement¹². For patients with active infection and suspected root abscess, median sternotomy is recommended. Furthermore, during IE surgery, it is critical to recognize that lesions may have progressed beyond what was initially expected in preoperative assessments.

This study retrospectively evaluates the clinical outcomes of patients with acute IE of the aortic valve based on the surgical approach used.

Figure 1a: Incision of right lateral mini-thoracotomy approach in our institute.

Materials and Methods

Patient selection

We retrospectively reviewed 13 patients with acute IE in the aortic valve treated at our hospital between August 2015 and March 2022. All patients were diagnosed with acute IE based on modified Duke criteria^13,14. The exclusion criteria were IE that healed during the chronic phase and prosthetic valve endocarditis. Patients were evaluated as having root abscess or not with preoperative computed tomography (CT) or transesophageal echocardiographic images. We evaluated the preoperative patient background, intraoperative procedure, and postoperative outcomes of patients.

Data collection

The following patient demographics and comorbidities were recorded: age, sex, diabetes mellitus, chronic renal disease requiring hemodialysis, immunosuppressive drug administration, history of cardiac surgery, history of coronary artery disease, history of cerebrovascular disease, and emergency cases. Furthermore, the following preoperative data related to IE and cardiac function were collected: duration from onset to diagnosis, duration from diagnosis to surgery, causative microorganisms (such as Staphylococcus and Streptococcus), thrombi in other organs, and preoperative echocardiographic data. All patients underwent transthoracic echocardiography. Echocardiographic data included IE-related valve regurgitation and perivalvular lesions, which were defined as the presence of abscesses, pseudoaneurysms, or fistulas. Other organ embolisms were excluded based on the enhanced CT imaging. Preoperative cerebral complications were defined as fresh lesions such as cerebral infarction, cerebral hemorrhage, subarachnoid hemorrhage, or intracranial mycotic aneurysms.

Based on blood culture results, antibiotics were administered according to the recommendations of the infection control team at our institute. Indications for valve surgery included heart failure that was unresponsive to medical therapy, persistent infection, repeat embolization, high embolic risk, and perivalvular extension of IE. Emergency cases were defined as patients who could not be treated with antibiotics for 3 weeks before surgery according to guideline recommendations and who had to undergo surgery because of heart failure, controlled infection, giant vegetations, or valve annular abscesses. Postoperative antibiotics were administered for 6 or 4 weeks if the intraoperative culture was positive or negative, respectively. In patients with severe intraoperative infection, oral antibiotics were continued for at least 1 year after discharge.

Surgical procedure

The Society of Thoracic Surgeons defines MICS as “any procedure not performed with a full sternotomy and cardiopulmonary support”^{7, 8}.

Mini-sternotomy and right anterior thoracotomy are widely used approaches for MICS-aortic valve replacement (MICS-AVR) worldwide. However, due to anatomical limitations and specific complications associated with these methods, right lateral mini-thoracotomy has recently gained popularity in Japan. This approach offers advantages such as improved surgical visualization and reduced intraoperative bleeding compared to the right anterior mini-thoracotomy^10,15,16. At our institution, MICS using right lateral mini-thoracotomy has already been introduced for isolated aortic and mitral valve repair when deemed anatomically feasible. Anatomical feasibility was defined as the possibility to perform peripheral cannulation, the diameter of an ascending aorta not exceeding 4 cm, and the absence of adhesions in the right pleural space. Additionally, the MICS approach was used only in cases with localized infection. Therefore, this approach was considered for some selected cases of IE.

As part of the standard anesthetic protocol for all sternum-sparing MICS-AVR, the airway was intubated with a double-lumen ventilation tube, allowing single-lung ventilation. A conventional surgical cut-down was utilized for the exposure of femoral vessels being cannulated under transesophageal echocardiography guidance and X-ray vision to establish cardiopulmonary bypass. The patient is placed in the supine position with the right side of the chest slightly elevated by pillows and the right arm raised and attached to an armrest of the operating table. A 7cm incision is made along the right anterior axillary line (Fig. 1a), and subsequent dissection of the serratus anterior and intercostal muscle is carried out to access the third or fourth intercostal space. After vacuum-assisted cardiopulmonary bypass was established, a left ventricular vent was placed through the right superior pulmonary vein, and the patients were cooled to 32 C. The ascending aorta was clamped and antegrade or retrograde cardioplegic solution was given using cold blood cardioplegia.

In a median sternotomy, vacuum-assisted cardiopulmonary bypass or systemic cooling were not performed. For patients with root abscesses, a median sternotomy was performed (Fig. 1b and 1c).

Figure 1b: Preoperative CT imaging showing root abscess (black dotted circle). CT, computed tomography

Figure 1c: Preoperative transesophageal echocardiography showing echo free space indicating root abscess (white dotted circle).

The abscess was thoroughly debrided, and if it was confined to a single leaflet and the endocardium (Fig. 2a), patch closure was performed (Fig. 2b); after debridement, the cavity was closed using a bovine pericardial patch, followed by aortic valve replacement (AVR). If the abscess extended to the intervalvular fibrosa and aorto-mitral discontinuity was suspected, the Commando technique was considered. In cases where the abscess extended deep into the aortic root, leading to aortic valve dehiscence, aortic root replacement was performed. 

Figure 2a: Intraoperative view showing root abscess (white dotted circle) and defect with large vegetation in noncoronary one leaflet (white arrow).

Figure 2b: Intraoperative view showing reconstruction of the defect to make new annulus using bovine pericardium patch (white arrow).

Outcome measures

The primary outcome was all-cause mortality. The secondary outcomes were major adverse cardiac and cerebrovascular events (MACCE) and events related to recurrent infection. MACCE were defined as the composite of all-cause mortality, hospitalization due to heart failure, repeat cardiac surgery, and brain-related events, including cerebral hemorrhage or stroke.

Statistical analysis

Continuous and categorical variables are expressed as mean ± standard deviation or median (range) and number (percentage) of patients, respectively. Categorical variables were analyzed using Fisher’s exact test, continuous variables were compared using Student’s t-test, and non-parametric variables were analyzed using the Mann–Whitney U test. All data analyses were performed using the JMP 17.1 software (SAS Institute, Cary, NC, USA). Statistical significance was set at p < 0.05.

Results

Table 1 summarizes the patients’ preoperative clinical characteristics including age, sex, duration from onset to diagnosis, duration from diagnosis to surgery, mean body surface area, mean body mass index, diabetes mellitus, immunosuppressive drug administration, chronic renal disease requiring hemodialysis, preoperative ejection fraction, prosthetic valve endocarditis, causative microorganisms (e.g., *Streptococcus*),  thrombi in other organs, cerebral complications, New York Heart Association class, brain natriuretic peptide level, and Euro score. Annular abscesses were observed in five cases (38%); however, the infection was localized to a single leaflet and the endocardium, allowing for repair with a bovine pericardial patch. During the study period, no cases required the Commando technique or aortic root replacement. Emergency surgery was performed in seven cases (54%).

Table 2 presents the procedural characteristics, success rates, and related parameters. All six patients eligible for right lateral mini-thoracotomy approach completed the surgery without converting to a median sternotomy. All patients were weaned from cardiopulmonary bypass. One patient required a tracheostomy due to postoperative cerebral bleeding. No cases of wound infection or postoperative bleeding complications were observed.

The median follow-up period was 421 days (range, 20–2030 days). No 30-day or late mortality was observed. In one patient underwent the right lateral mini-thoracotomy approach, left ventricular diverticulum was revealed by multidetector CT after surgery (Fig. 3a), which could not be detected by preoperative CT (Fig. 3b) or intraoperative view (Fig. 3c) and transesophageal echocardiography. MACCE occurred in two patients: one developed cerebral hemorrhage, and another underwent repeat mitral valve surgery due to worsening regurgitation. Infection-related complications occurred in three patients, including cerebral hemorrhage from a ruptured mycotic aneurysm, a late-phase brain abscess, and a ruptured mycotic splenic artery aneurysm requiring interventional treatment. No IE-related cardiac events were observed.

Figure 3a: Postoperative multidetector CT showing intraventricular septal space (white arrow). CT, computed tomography.

Figure 3b: Preoperative CT imaging showing no abnormal change

Figure 3c: Intraoperative view via right lateral mini-thoracotomy approach showing no abnormal changes in the left ventricular outflow tract.

No recurrence of IE was observed in the five cases of aortic root repair using a bovine pericardial patch via median sternotomy. 

Discussion

As no all-cause mortality or IE-related cardiac events were observed, our surgical strategy for IE in the aortic valve was appropriate. All six patients who underwent the right lateral mini-thoracotomy approach completed the procedure without critical complications. Avoiding median sternotomy is particularly advantageous for patients with IE. However, MICS should be carefully selected in IE cases, as unexpected infection spread, or structural abnormalities may be discovered intraoperatively. While preoperative CT is useful¹⁷, it is not entirely reliable, as infection can progress unpredictably before surgery. The primary goal in IE treatment is complete resection of infected tissue; therefore, MICS should be limited to cases where the infection is confined to the aortic valve leaflet.

In one case, a ventricular diverticulum was detected postoperatively. Isolated congenital cardiac diverticula in the subaortic valve area generally follow a benign course but may lead to complications such as spontaneous rupture or endocarditis¹⁸. Holzhey et al. reported that reoperation for bleeding may be a disadvantage of the right mini-thoracotomy approach, likely due to the limited direct visualization of the entire operative field⁴. Furthermore, the restricted surgical view in this approach makes repair procedures challenging. If abnormal structures or unexpected infection progression are identified intraoperatively, the limited working space may hinder adequate debridement and patch repair.

MICS-AVR has been shown to decrease postoperative complications, providing faster recovery, a shorter hospital length of stay, less pain, better aesthetic results, and, consequently, less use of hospital resources^19-23. It enables effective early social reintegration, because it does not require either sternotomy or limitations in postoperative exercise. Significantly lower rates of postoperative impaired wound healing were noted in the MICS-AVR via a right lateral mini-thoracotomy approach group as it is bone-sparing and does not involve the shoulder girdle²⁴. Furthermore, there is no possibility of local blood supply being impaired due to transection of the right mammary artery caused by right anterior thoracotomy²⁴. However, the minimally invasive approach limits the ability to control left ventricular distention, and some surgeons do not use it for severe aortic insufficiency²⁵.

According to Ito et al., while the ascending aorta is relatively distant in the right lateral mini-thoracotomy approach, the wide intrathoracic space can serve as an effective working area with endoscopic assistance¹⁵. However, in a direct vision approach via right lateral mini-thoracotomy, the usable working space remains limited, and the distance to the ascending aorta poses additional challenges. Wilbring et al. reported that a perpendicular view of the aortic valve can typically be established after placing aortic stay sutures²⁶. Further advancement in total endoscopic MICS techniques with some method to make good surgical field and equipment is desirable to enhance feasibility. Additionally, in some cases, performing preoperative multidetector CT or transesophageal echocardiography may be difficult. If unexpected intraoperative findings arise, conversion to median sternotomy should not be delayed. In the steadfast belief that sacrificing patient safety in favor of limited skin incisions is unconscionable and that minimally invasive surgery must at least be as safe as conventional surgery. Therefore, careful patient selection is essential when considering the lateral mini-thoracotomy approach for aortic valve IE.

Study limitations

This study has some limitations. First, the study sample size was small because of the rarity of the condition. Second, this was a retrospective single-center study without randomization. Third, there was no critical cases who indicated commando procedure or root replacement. Further, some patients did not undergo preoperative multidetector CT for detailed aortic root evaluation.

Conclusion

For patients with localized infection confined to the aortic valve leaflet, the right lateral thoracotomy approach is a feasible and effective minimally invasive option. However, careful patient selection is essential when considering MICS for infective endocarditis.

Declarations

Ethics approval and consent to participate

All study procedures were performed in accordance with the tenets of the Declaration of Helsinki. The Ethics Committee of Aichi Medical University Hospital approved this study on October 18, 2023 (approval number 2023-516). All the patients provided written informed consent for the use of their clinical data in scientific presentations or publications.

Consent for publication

Patients provided consent for the publication of this study. The patients’ identities were protected.

Funding

Not applicable

Competing interests

Kayo Sugiyama, Hirotaka Watanuki, Masato Tochii, and Katsuhiko Matsuyama have no conflicts of interest. The authors did not receive any financial support for this study.

Data availability

The datasets used and/or analyzed in the current study are available from the corresponding author upon reasonable request.

Authors' contributions　

Study conception: KS; Data collection: KS; Analysis: KS, KM; Investigation: KS; Writing: KS; Funding acquisition: KS; Critical review and revision: all authors; Final approval of the manuscript: all authors; Accountability for all aspects of the work: all authors. All the authors have read and approved the final version of the manuscript.

Acknowledgments　

We thank Honyaku Center, Inc. for English language editing. We also thank our colleagues for their helpful comments.

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