Minimally Invasive Valvular Surgery in the Elderly　― Safety, Early Recovery, and Long-Term Outcomes ―

Abstract

Background: For elderly people, the benefit of minimally invasive cardiac surgery (MICS) is unclear, so we evaluated the safety, recovery, and long-term survival in elderly MICS patients.

Methods and Results: 63 propensity score-matched pairs of 213 consecutive patients (≥70 years old) who underwent mitral and/or tricuspid valve surgery between 2010 and 2020 (121 right mini-thoracotomies vs. 92 full sternotomies) were compared. The primary outcome was safety (composite endpoint of in-hospital death or major complication). Secondary outcomes were early ambulation and discharge to home. There were no differences between the groups for in-hospital death (3.2% vs. 0.0%, P=0.157) and primary outcome (14.3% vs. 17.5%, P=0.617). The rate of early ambulation (73.0% vs. 55.6%, P=0.048) and discharge to home (66.7% vs. 49.2%, P=0.034) were significantly higher in the mini-thoracotomy group. Major complication was an independent negative predictor of early ambulation for mini-thoracotomy but not for a conservative approach. Survival was 87.8±4.4% vs. 86.8±4.7% at 5 years, which was not significantly different.

Conclusions: Similar safety but better recovery were observed for mini-thoracotomy, and long-term survival was comparable between groups. Major complication was a negative predictor of early ambulation after mini-thoracotomy. Careful preoperative risk stratification would enhance the benefits of MICS in elderly patients.

The advantages of the right mini-thoracotomy approach over standard full sternotomy have been reported,^1–3 but may be limited for elderly patients because of concerns about perioperative complications such as stroke and aortic dissection.^4–6 Thus, the benefits of minimally invasive valvular surgery for elderly patients has not been fully appraised.^6–9

We compared the outcomes of atrioventricular valvular surgery with the right mini-thoracotomy approach vs. standard full sternotomy in patients aged ≥70 years to clarify the safety, recovery process, and long-term survival of the minimally invasive technique for elderly patients.

Methods

Study Population

This retrospective observational study was approved by the Nagasaki University Hospital institutional review board, and the need to obtain informed consent was waived (approval no. 22041814, 26 April 2022).

We analyzed the data for 213 patients ≥70 years of age who underwent isolated mitral or tricuspid valve surgery or who double-valve surgery with or without pulmonary vein isolation between March 2010 and December 2020 (121 right mini-thoracotomies vs. 92 full sternotomies). The distribution of patients’ ages is shown in Figure 1. The primary outcome was safety, defined as a composite endpoint of in-hospital death or major complication. Major complication in this study comprised stroke (central neurologic deficit persisting >72 h); prolonged ventilation (>24 h); new requirement for hemodialysis; aortic dissection during surgery; and reoperation for any reason. Secondary outcomes were the rates of early ambulation (≤3 days after surgery) and discharge to home.

Figure 1.

Number of patients per age by surgical approach. Patients were significantly younger in the right mini-thoracotomy group compared with the full sternotomy group (75.8±4.5 vs. 77.8±4.2, P<0.001). The highest age in this study was 92 years and that patient underwent mitral valve repair by the right mini-thoracotomy approach.

Selection of Surgical Approach

The optimal approach was selected for each patient based on the results of preoperative examinations, including computed tomography (CT), angiography, echocardiography, pulmonary function testing, and cardiac catheterization or coronary CT. The main exclusion criteria for the right mini-thoracotomy approach were a previous history of right thoracotomy, greater than moderate aortic regurgitation, arteriosclerosis obliterans, thoraco-abdominal aortic aneurysm, congestive heart failure with pulmonary hypertension, severe left or right ventricular dysfunction, pectus excavatum, and history of lung disease such as interstitial pneumonia and pneumothorax.¹⁰ Limited numbers of patients were selected for mini-thoracotomy when we started using this approach in 2010, but have steadily increased with experience (Figure 2). Right mini-thoracotomy was initially selected for patients with isolated mitral valve disease who were <70 years old without significant aortic, iliac, or femoral disease that prevented safe retrograde arterial perfusion, or respiratory disease. As technical expertise increased, the right mini-thoracotomy approach was selected for patients aged ≥70 years old, and applied to double-valve surgery of mitral and tricuspid valve disease. The right mini-thoracotomy approach was generally selected, even for the elderly, if there were no relative contraindications.¹⁰

Figure 2.

Number of surgeries per year by surgical approach. The overall number of surgeries has increased, especially since 2014, with a significant increase in the use of right mini-thoracotomy approach.

Surgical Techniques

The right mini-thoracotomy was performed via the 4th intercostal space using a 5-cm skin incision. Cardiopulmonary bypass was established using right femoral artery perfusion and venous drainage through the right internal jugular and right femoral veins. From September 2015, the arterial perfusion strategy was changed to a double-route perfusion using the femoral artery and a right brachial artery to prevent retrograde aortic dissection and stroke. The ascending aorta was cross-clamped using Chitwood-type forceps via the 3rd intercostal space. In patients who underwent standard full sternotomy, cardiopulmonary bypass was established via ascending aorta perfusion and bicaval drainage. Mitral valve repair was performed using the restoration technique (triangular resection and neo-chordal reconstruction combined with annuloplasty).¹¹ Tricuspid valve annuloplasty was performed using semi-rigid prosthetic rings. For severe functional tricuspid regurgitation with tethered leaflets, spiral suspension was performed with annuloplasty.¹² Mitral or tricuspid valve replacement was performed using a biological prosthesis. Pulmonary vein isolation was conducted using a CryoProbe at −60℃ for 2 min. Local intercostal nerve block was performed at the end of surgery, and a continuous postoperative extrapleural intercostal nerve block (CEINB) was applied for 3 days in the right mini-thoracotomy group. The CEINB catheter was placed in the extrapleural intercostal nerve area through the end of the thoracotomy incision. Ropivacaine (0.2%) was continuously administered at 4 mL/h using a disposable continuous infuser. Loxoprofen (180 mg/day) was the postoperative analgesic, and in cases of renal dysfunction, acetaminophen (1,500–2,000 mg/day) was administered in both groups.

Postoperative Rehabilitation

Our rehabilitation program conformed to Japanese Circulation Society guidelines.¹³ Rehabilitation started on postoperative day 1 based on the patient’s condition. The main exclusion criteria for rehabilitation were low output syndrome, tachycardia (heart rate ≥120 beats/min), new arrhythmia (atrial fibrillation or premature ventricular contraction greater than grade 4a using the Lown classification), tachypnea (≥30 beats/min), and bleeding after surgery. The rehabilitation protocols for both groups were the same.

Follow-up

Patients were followed up in the outpatient clinic or by the referring cardiologist. A medical interview by telephone was conducted for patients who could not participate in outpatient clinic follow-up. Postoperative events were evaluated according to the American Association for Thoracic Surgery, European Association for Thoracic Surgery, and Society of Thoracic Surgeons guidelines.¹⁴ Study follow-up ended on September 30, 2021, and 1 patient (from the right mini-thoracotomy group) was lost to follow-up (follow-up rate, 99.5%). All patients underwent anticoagulation therapy with warfarin sodium for 3 months after surgery. Warfarin treatment was continued in patients with atrial fibrillation. Patients with biological prostheses received aspirin treatment for 3 months after surgery.

Statistical Analysis

Continuous data are reported as the mean±standard deviation or median (interquartile range), and categorical variables are reported as percentages. Differences between unmatched groups were assessed using Student’s t-test and Chi-square test or Fisher’s exact test, as appropriate. To balance the distribution of baseline risk factors between groups, propensity score (PS) matching was performed, with the PS estimated using a multivariable logistic regression model, for which the independent variables were age, predominant valve lesion (mitral or tricuspid), etiology of mitral valve disease, current congestive heart failure, and clinical frailty scale. We used a nearest matching algorithm with a caliper index of 0.2. The outcomes in the matched groups were then compared using Student’s t-test for dependent variables or McNemar’s test, as appropriate. Predictors of early ambulation were selected from among clinically important factors. Multivariable logistic analysis was performed to detect independent factors for early ambulation. Variables included right mini-thoracotomy approach, preoperative atrial fibrillation (AF), clinical frailty scale, cardiopulmonary bypass time, and major complication. For long-term survival, Kaplan-Meier curves were calculated and compared using the log-rank test (unmatched data) and Cox regression analysis (matched data). A P value <0.05 was considered significant. Analyses were conducted using JMP version 14.0 (SAS Institute Inc., Cary, NC, USA).

Results

Duration of Follow-up

Follow-up was significantly longer in the standard full sternotomy group than in the right mini-thoracotomy group (4.6 [2.1–7.0] years vs. 3.0 [1.6–4.8] years, P≤0.001).

Preoperative Patient Characteristics

Table 1 summarizes the baseline clinical and operative characteristics of the study population before and after PS matching. After PS matching 63 patients in each group, no differences in demographic data were observed except for the prevalence of preoperative AF.

Table 1. Preoperative Patient Characteristics

	Overall			Propensity-matched patients
	Right mini-thoracotomy (n=121)	Full sternotomy (n=92)	P value	Right mini-thoracotomy (n=63)	Full sternotomy (n=63)	P value
Age, years	75.8±4.5	77.8±4.2	<0.001	77.0±4.6	77.2±4.1	0.741
Sex, female	66 (54.6%)	53 (57.6%)	0.656	39 (62.0%)	36 (57.1%)	0.602
Body mass index, kg/m2	21.9±3.2	21.7±3.7	0.756	21.8±3.3	21.8±3.3	0.901
Reoperation	18 (14.9%)	12 (13.0%)	0.703	11 (17.5%)	6 (9.5%)	0.225
Predominant valve lesion
Mitral	116 (95.9%)	82 (89.1%)	0.064	59 (93.7%)	59 (93.7%)	>0.99
Tricuspid	5 (4.1%)	10 (10.9%)		4 (6.4%)	4 (6.4%)
Etiology of mitral valve disease
Degenerative	78 (64.5%)	56 (60.9%)	0.005	41 (65.1%)	43 (68.3%)	0.824
Atrial	18 (14.9%)	4 (4.3%)		4 (6.4%)	4 (6.4%)
Rheumatic	11 (9.1%)	6 (6.5%)		9 (14.3%)	6 (9.5%)
Infective endocarditis	4 (3.3%)	15 (16.3%)		3 (4.8%)	3 (4.8%)
Cardiomyopathy	4 (3.3%)	5 (5.4%)		3 (4.8%)	2 (3.2%)
Other	6 (5.0%)	6 (6.5%)		3 (4.8%)	5 (7.9%)
Current CHF	23 (19.0%)	37 (40.2%)	<0.001	14 (22.2%)	15 (23.8%)	0.819
LVEF, %	63.2±13.7	64.4±12.7	0.524	62.9±15.3	65.1±11.6	0.325
Atrial fibrillation	57 (47.1%)	53 (57.6%)	0.129	31 (49.2%)	40 (63.5%)	0.039
Hypertension	51 (42.2%)	36 (39.1%)	0.657	27 (42.9%)	29 (46.0%)	0.683
Diabetes mellitus	24 (19.8%)	22 (23.9%)	0.474	13 (20.6%)	15 (23.8%)	0.617
Hyperlipidemia	35 (28.9%)	20 (21.7%)	0.235	20 (31.8%)	12 (19.1%)	0.117
Serum creatinine, mg/dL	1.00±0.35	1.14±0.47	0.067	1.02±0.37	1.08±0.47	0.403
Hemodialysis	3 (2.5%)	2 (2.2%)	>0.99	0 (0.0%)	0 (0.0%)	–
Peripheral vascular disease	4 (3.3%)	7 (7.6%)	0.214	2 (3.2%)	5 (7.9%)	0.257
History of CVA	5 (4.1%)	7 (7.6%)	0.371	1 (1.6%)	3 (4.8%)	0.317
COPD	0 (0.0%)	5 (5.4%)	0.014	0 (0.0%)	0 (0.0%)	–
Clinical frailty scale	3.6±1.0	4.4±1.6	<0.001	3.9±1.0	3.9±1.2	0.766
Well (scale 1–2)	10 (8.3%)	1 (1.1%)	<0.001	2 (3.2%)	0 (0.0%)	0.796
Pre-frail (scale 3–4)	94 (77.7%)	55 (59.8%)		47 (74.6%)	50 (79.4%)
Frail (scale 5+)	17 (14.1%)	36 (39.1%)		14 (22.2%)	13 (20.6%)
EuroSCORE II	3.30 (2.32–5.20)	5.21 (3.10–9.37)	<0.001	3.82 (2.53–6.28)	3.99 (2.68–6.35)	0.681
JapanSCORE	2.00 (1.55–3.25)	3.25 (2.00–7.30)	0.002	2.60 (1.80–4.40)	2.50 (1.90–5.60)	0.766

CVA, cerebrovascular accident; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; LVEF, left ventricular ejection fraction.

PS-Matched Comparison of Surgical Procedure and Operative Data

Table 2 shows the surgical procedure and operative data. Among PS-matched patients, both the time of surgery (317±83 vs. 260±55 min, P<0.001) and of cardiopulmonary bypass perfusion (166±51 vs. 139±36 min, P=0.003) were significantly longer in the right mini-thoracotomy group.

Table 2. Surgical Procedure and Operative Data

	Overall			Propensity-matched patients
	Right mini-thoracotomy (n=121)	Full sternotomy (n=92)	P value	Right mini-thoracotomy (n=63)	Full sternotomy (n=63)	P value
Isolated tricuspid valve surgery	5 (4.1%)	9 (9.8%)	0.102	4 (6.4%)	4 (6.4%)	0.384
Isolated mitral valve surgery	70 (57.9%)	41 (44.6%)		34 (54.0%)	29 (46.0%)
Mitral and tricuspid surgery	46 (38.0%)	42 (45.7%)		25 (39.7%)	30 (47.6%)
Mitral valve repair	94 (77.7%)	64 (69.6%)	0.180	43 (68.3%)	47 (74.6%)	0.394
Pulmonary vein isolation	39 (32.2%)	21 (22.8%)	0.131	16 (25.4%)	19 (30.2%)	0.549
Operation time, min	329.8±107.8	267.5±56.7	<0.001	316.8±82.6	260.3±54.6	<0.001
Cardiopulmonary bypass time, min	176.2±57.4	143.7±37.5	<0.001	165.8±50.7	139.3±35.6	0.003
Cross-clamp time, min	101.6±33.9	87.2±28.8	0.001	95.1±32.7	85.9±27.1	0.109
Blood transfusion	102 (84.3%)	85 (92.4%)	0.074	55 (87.3%)	57 (90.5%)	0.564

PS-Matched Comparison of Outcomes

The outcomes are shown in Table 3. In-hospital mortality was 3.2% vs. 0.0% (P=0.157) and the primary outcome was 14.3% vs. 17.5% (P=0.617) for the right mini-thoracotomy and standard full sternotomy group, respectively. The rate of independent ambulation at postoperative days 1–5 is shown in Figure 3. The rate of early ambulation within 3 days after surgery was significantly higher in the right mini-thoracotomy group than in the standard full sternotomy group (73.0% vs. 55.6%, P=0.048). The rate of discharge to home was significantly higher in the right mini-thoracotomy group than in the standard full sternotomy group (66.7% vs. 49.2%, P=0.034). The postoperative hospital length of stay tended to be shorter in the right mini-thoracotomy group compared with the standard full sternotomy group (21.0 [18.0–28.0] vs. 22.0 [19.0–36.0] days, P=0.090). Although there was no significant difference in complications between the PS-matched groups, there were 2 cases of aortic dissection in the right mini-thoracotomy group before PS matching but none in the standard full sternotomy group. The diameter of the ascending aorta in the 2 patients with aortic dissection was 48 mm and 35 mm, respectively. The first case was an ascending aorta cross-clamp-related dissection, and the second case was a retrograde arterial perfusion-related dissection. A total of 4 patients, 2 with aortic dissection described above and 2 with intraoperative bleeding, were converted from right mini-thoracotomy to full sternotomy.

Table 3. Outcomes

	Overall			Propensity-matched patients
	Right mini-thoracotomy (n=121)	Full sternotomy (n=92)	P value	Right mini-thoracotomy (n=63)	Full sternotomy (n=63)	P value
Duration of follow-up, years	3.0 (1.6–4.8)	4.6 (2.1–7.0)	<0.001	3.3 (1.6–5.1)	5.4 (3.7–7.2)	<0.001
30-day mortality	2 (1.7%)	2 (2.2%)	>0.99	1 (1.6%)	0 (0.0%)	0.317
Hospital mortality	3 (2.5%)	2 (2.2%)	>0.99	2 (3.2%)	0 (0.0%)	0.157
Intubation time, h	6.0 (4.0–13.0)	9.5 (5.0–22.0)	0.379	6.0 (4.0–14.0)	7.0 (5.0–16.0)	0.265
ICU length of stay, h	21.0 (19.0–44.0)	46.0 (22.0–92.0)	0.001	26.0 (20.0–45.0)	43.0 (21.5–65.0)	0.108
Hospital length of stay, days	20.0 (16.0–26.0)	25.0 (20.0–43.8)	0.011	21.0 (18.0–28.0)	22.0 (19.0–36.0)	0.090
Discharge to home	89 (73.6%)	40 (43.5%)	<0.001	42 (66.7%)	31 (49.2%)	0.034
Time to independent ambulation, days	2.0 (2.0–3.0)	4.0 (3.0–6.0)	0.001	3.0 (2.0–4.0)	3.0 (2.0–5.0)	0.038
<1	18 (14.9%)	1 (1.1%)	<0.001	7 (11.1%)	1 (1.6%)	0.034
<3	93 (76.9%)	43 (46.7%)	<0.001	46 (73.0%)	35 (55.6%)	0.048
<5	110 (90.9%)	63 (68.5%)	<0.001	56 (88.9%)	51 (81.0%)	0.197
WBC, /μL	11,696±4,462	13,442±5,290	0.012	11,810±5,588	12,905±3,481	0.194
CRP, mg/dL	15.1±5.1	16.8±5.8	0.024	15.1±5.2	16.5±6.0	0.067
Major complications	17 (14.1%)	23 (25.0%)	0.043	9 (14.3%)	11 (17.5%)	0.617
Prolonged ventilation >24 h	10 (8.3%)	20 (21.8%)	0.005	4 (6.4%)	9 (14.3%)	0.132
Reoperation for any reason	6 (5.0%)	7 (7.6%)	0.565	4 (6.4%)	4 (6.4%)	>0.99
New dialysis required	3 (2.5%)	6 (6.5%)	0.179	3 (4.8%)	2 (3.2%)	0.655
Stroke	1 (0.8%)	3 (3.3%)	0.318	0 (0.0%)	2 (3.2%)	0.157
Aortic dissection during surgery	2 (1.7%)	0 (0.0%)	0.507	1 (1.6%)	0 (0.0%)	0.317
Other complications
Atrial fibrillation (new onset)	12 (9.9%)	17 (18.5%)	0.071	6 (9.5%)	12 (19.1%)	0.157
Reoperation for bleeding	5 (4.1%)	5 (5.4%)	0.749	4 (6.4%)	4 (6.4%)	>0.99
Prolonged ventilation >72 h	3 (2.5%)	9 (9.8%)	0.022	1 (1.6%)	4 (6.4%)	0.180
Pacemaker implant	4 (3.3%)	3 (3.3%)	>0.99	2 (3.2%)	2 (3.2%)	>0.99
Conversion to sternotomy	4 (3.3%)	0 (0.0%)	0.135	2 (3.2%)	0 (0.0%)	0.157
Low output syndrome	1 (0.8%)	4 (4.4%)	0.169	1 (1.6%)	1 (1.6%)	>0.99
Lymphocele	3 (2.5%)	0 (0.0%)	0.260	1 (1.6%)	0 (0.0%)	0.317
Deep sternal infection	0 (0.0%)	1 (1.1%)	0.432	0 (0.0%)	1 (1.6%)	0.317
Re-expansion lung edema	0 (0.0%)	0 (0.0%)	–	0 (0.0%)	0 (0.0%)	–

CRP, C-reactive protein; ICU, intensive care unit; WBC, white blood cells.

Figure 3.

Postoperative ambulatory rates from postoperative day (POD) 1–5. The rate at POD 1 and 3 was significantly higher in the right mini-thoracotomy group compared with the standard full sternotomy group (POD 1: 11.1% vs. 1.6%, P=0.03; POD 3: 73.0% vs. 55.6%, P=0.05).

Predictors of Early Ambulation

Table 4 shows the results of multivariable logistic regression analysis for early ambulation within 3 days after surgery. Overall, the right mini-thoracotomy approach was the independent positive factor for early ambulation after surgery, while clinical frailty scale and major complication were negative predictors. In the right mini-thoracotomy group, clinical frailty scale and major complication were negative predictors. The 121 patients in the right mini-thoracotomy group were divided into 3 groups according to the clinical frailty scale (well, scale 1–2; pre-frail, 3–4; frail, 5–9). As the clinical frailty scale score increased, the rate of early ambulation within 3 days after surgery significantly decreased (10/10 patients, 100.0% vs. 73/94 patients, 77.7% vs. 10/17 patients, 58.8%, respectively; P=0.046). However, in the standard full sternotomy group, clinical frailty scale was the only negative predictor, and major complication was not a negative predictor.

Table 4. Univariate and Multivariable Logistic Regression Analyses of Parameters for Predicting Early Ambulation (Within 3 Days After Surgery): (A) All Patients; (B) By Surgical Approach

(A)	All patients
	Univariate analysis		Multivariate analysis
	OR (95% CI)	P value	OR (95% CI)	P value
Right mini-thoracotomy approach	3.79 (2.10–6.82)	<0.001	3.69 (1.76–7.72)	<0.001
Atrial fibrillation	0.77 (0.44–1.35)	0.356	0.99 (0.50–1.98)	0.975
Clinical frailty scale	0.52 (0.41–0.70)	<0.001	0.58 (0.44–0.78)	<0.001
Cardiopulmonary bypass time	1.00 (0.99–1.00)	0.131	0.99 (0.99–1.00)	0.034
Major complication	0.15 (0.07–0.32)	<0.001	0.22 (0.09–0.52)	<0.001
(B)	Right mini-thoracotomy (n=121)				Full sternotomy (n=92)
	Univariate analysis		Multivariate analysis		Univariate analysis		Multivariate analysis
	OR (95% CI)	P value	OR (95% CI)	P value	OR (95% CI)	P value	OR (95% CI)	P value
Clinical frailty scale	0.49 (0.31–0.78)	0.003	0.44 (0.26–0.75)	0.003	0.61 (0.45–0.83)	<0.001	0.65 (0.47–0.90)	0.010
Cardiopulmonary bypass time	0.99 (0.98–1.00)	0.003	0.99 (0.98–1.00)	0.083	0.99 (0.98–1.01)	0.278	1.00 (0.98–1.01)	0.448
Major complication	0.11 (0.04–0.33)	<0.001	0.13 (0.03–0.46)	0.002	0.23 (0.08–0.68)	0.008	0.34 (0.10–1.09)	0.069

CI, confidence interval; OR, odds ratio.

PS-Matched Comparison of Long-Term Survival

Figure 4 shows that the long-term survival of the PS-matched patients in the right mini-thoracotomy and standard full sternotomy groups (87.8±4.4% vs. 86.8±4.7% at 5 years and 71.0±11.3% vs. 56.9±10.2% at 10 years, respectively) was not significantly different (Cox regression: hazard ratio 0.99; 95% confidence interval 0.43–2.31; P=0.983).

Figure 4.

Long-term survival for matched patients. Survival in the right mini-thoracotomy group and the standard full sternotomy group was 87.8±4.4% vs. 86.8±4.7% at 5 years and 71.0±11.3% vs. 56.9±10.2% at 10 years, respectively, which was not significantly different (Cox regression: hazard ratio 0.99; 95% confidence interval 0.43–2.31; P=0.98). F/U, follow-up.

Discussion

There are few reports on the safety of right mini-thoracotomy compared with standard full sternotomy in elderly patients.^6,7 Holzhey et al performed a PS analysis and reported no significant differences in 30-day mortality rate (7.7% vs. 6.3%) or incidence of major adverse cardiac/cerebrovascular events (11.2% vs. 12.6%) in patients aged ≥70 years who underwent mitral valve surgery.⁶ However, Lamelas et al investigated the outcomes of isolated aortic valve replacement or mitral valve surgery in patients aged ≥75 years, and reported that the in-hospital mortality rate (1.7% vs. 9.5%) and incidence of major morbidity were significantly lower with the right mini-thoracotomy approach.⁷ The present study demonstrated no significant differences between groups in in-hospital deaths or primary outcome, which suggested that the right mini-thoracotomy approach is as safe as standard full sternotomy in patients aged ≥70 years. The postoperative hospital length of stay tended to be shorter in the right mini-thoracotomy group, but was longer when compared with previous studies.^1,7 This long hospitalization may be related to differences in the medical insurance system between Japan and other countries. Geographic factors and the residential environment in Nagasaki Prefecture are also assumed to contribute to long hospitalization. Nagasaki Prefecture has the largest number of isolated islands in Japan, and Nagasaki City is a town with many steep hills. For these reasons, the elderly are anxious about leaving the hospital because they do not have easy access to a hospital after discharge, and they often request an extension of their hospital stay regardless of the surgical procedure.

In this study, major complication was an independent negative predictor of early ambulation in the right mini-thoracotomy group. Proper patient selection is crucial to ensure the safety of the right mini-thoracotomy approach, especially in elderly patients who are more likely to be at risk of vascular complications such as aortic dissection and stroke.¹⁰ Intraoperative aortic dissection,¹⁵ which was observed in this study, is reported to be associated with pre-existing aortic pathology such as atherosclerosis and cystic medial necrosis. An ascending aorta dilatation >40 mm represents a risk for aortic dissection,¹⁶ and the guideline for minimally invasive cardiac surgery recommends standard full sternotomy in such patients, especially those undergoing endoaortic balloon occlusion.¹⁰ The perfusion strategy to treat these complications is also controversial.^17–19 Retrograde arterial perfusion is reported to be associated with a higher incidence of stroke and aortic dissection compared with antegrade central aortic perfusion,^20,21 and some studies recommend central aortic perfusion.^18,20 We have used a 2-route perfusion strategy involving a combination of the right brachial and femoral arteries because 1 patient experienced stroke with the right mini-thoracotomy approach. Since beginning to use the 2-route strategy, no patient has developed vascular-related complications. The usefulness of brachial artery perfusion has already been reported in the aortic surgery field,²² because it offers various arterial perfusion routes in the right mini-thoracotomy approach for elderly patients.

A systematic review reported that frail patients had a higher likelihood of experiencing death, morbidity, and functional decline following cardiac surgery.²³ In the present study, the clinical frailty scale and major complication were independent negative factors for early ambulation in the right mini-thoracotomy group. The greater the frailty level, the greater the risk of a slow recovery after surgery. However, in the standard full sternotomy group, only the clinical frailty scale was an independent negative factor for early ambulation. This means that major complication prevents early ambulation, which is one of the most important advantages of the mini-thoracotomy approach in elderly people. A recent study using the Society of Thoracic Surgeons National Database also supports the advantages of minimally invasive valvular surgery for patients aged ≥65 years.²⁴ The right mini-thoracotomy approach enables early postoperative ambulation, which may promote rapid postoperative recovery, and it should be considered when older patients require atrioventricular valve surgery.^7,24 However, as our results showed, major complication negatively affects early ambulation, and therefore, in patients who are likely to be at risk of major complication, the standard full sternotomy approach may be considered because long-term survival was not inferior to the mini-thoracotomy approach. Nevertheless, it is evident that it is important to avoid major complication if the standard full sternotomy approach is selected.

Study Limitations

The main limitation of the present study is its retrospective design at a single institution. Even though we tried to compensate for potential bias in patient selection using PS matching, we were unable to adjust our selection criteria.

Conclusions

The safety of the right mini-thoracotomy approach in patients aged ≥70 years was similar to that of a standard full sternotomy, and the postoperative recovery course was faster than with standard full sternotomy. Atrioventricular valve surgery with right mini-thoracotomy is a promising approach to promoting rapid recovery, which is beneficial for selected elderly patients. However, the standard full sternotomy approach should be considered rather than mini-thoracotomy for elderly patients who are likely to be at risk of a major complication, especially vascular complications. Precise mini-thoracotomy-specific risk stratification and optimal use of minimally invasive procedures that reduce intra- or postoperative complications would maximize the benefit of minimally invasive cardiac surgery for elderly patients.

Acknowledgment

We gratefully acknowledge the assistance of Shuntaro Sato, PhD with the analyses.

Disclosures

The authors have no conflicts of interest to disclose.

IRB Information

This retrospective observational study was approved by the Nagasaki University Hospital institutional review board (approval no. 22041814, 26 April 2022).

Data Availability

The deidentified participant data and related study documents will be shared upon reasonable request to the corresponding author. Data requests will be accepted for up to 36 months after the publication of this article. For any purpose, the data will be shared as Excel files via E-mail.

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