Status of cardiovascular surgery in Japan between 2017 and 2018: A report based on the Cardiovascular Surgery Database. 2. Isolated coronary artery bypass surgery

Introduction

Coronary artery bypass grafting (CABG) has been a major procedure in open heart surgery for decades. Even though, according to the annual report of the Japanese Association for Thoracic Surgeons, the annual number of CABG procedures performed since 2002 has declined along with the decline in percutaneous coronary intervention cases, short- and long-term clinical outcomes and trends in strategy should be closely monitored to continue our efforts in pursuing better surgical results. This report presents short-term clinical outcomes of isolated CABG and details the graft choices in isolated CABG cases in 2017 and 2018 as per data registered in the Japan Cardiovascular Surgery Database (JCVSD).

Patients and methods

Perioperative clinical data derived from JCVSD registered cases of isolated CABG between January 2017 and December 2018 were retrospectively reviewed. Data extraction and presentation were similar to the previous biannual report from the JCVSD, for ease of data comparison.^1,2 We adopted the same definitions for comorbidities, postoperative complications, and terminologies utilized in the previous publication. ² JapanSCORE II is the most recent risk stratification model providing expected operative mortality and morbidities, which was calculated based on vast data registered with the JCVSD. The off-pump coronary artery bypass (OPCAB) and on-pump CABG data were compared using the chi-square test, with statistical significance defined as a p value < 0.05.

Results

Preoperative characteristics are presented in Table 1. The total number of patients included in the study was 26,913, which is an 8.4% decrease from the previous report (n = 29,395). ² A slight increase in chronic obstructive pulmonary disease (16.5% during the study period vs. 14.6% in 2015 and 2016) and renal replacement therapy cases (11.9% during the study period vs. 10.9% in 2015 and 2016) was noted in the characteristics of preoperative conditions. Table 2 presents case distributions by age and graft choices based on the pattern of internal thoracic artery (ITA) use (single ITA use as ‘SITA’, bilateral ITA use as ‘BITA’, and those without ITA use as ‘no ITA’) in combination with other types of graft: saphenous vein, radial artery (RA), and right gastroepiploic artery (GEA). Table 2-1 reports the above data for elective surgery. The number of patients continued to slightly shift towards older individuals, with 52.2% (n = 11,582) being over 70 years of age in this report compared to 50.5% in the previous report. ² The frequency of ITA use (SITA or BITA) was similar in patients < 60 years of age (SITA: 1,801 cases, BITA: 1,794 cases). BITA use was slightly more common in individuals over 60 years of age than in the previous report, with a SITA/BITA ratio of 1.75 (11,190/6,389 individuals) compared to 1.65 in the previous report. All arterial graft use in all age groups is presented in Table 2-1. For SITA, RA use slightly increased (587 vs. 422), whereas GEA use decreased (323 vs. 404) compared to the previous report. For BITA, RA use decreased (202 vs. 606), while GEA use remained relatively stable (799 vs. 806). Table 2-2 presents data for emergency and urgency cases. The frequency of BITA use was lower in emergency cases than in elective cases because of the extra time for harvesting ITA grafts. BITA use in emergency/urgency cases was 25.4%, compared to 36.9% in elective cases; however, BITA use slightly decreased in all age groups compared to the previous report. Table 3 shows graft choices for left anterior descending artery revascularization, stratified according to age. Left ITA was most frequently used (76.4% of patients), followed by right ITA (19.0% of patients); these results were similar to those in the previous report.

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Table 1.

Preoperative patient characteristics.

Year	2017		2018		Combined
No. of patients	13534		13379		26913
Male	10700	79.1%	10582	79.1%	21282	79.1%
Obese	3234	23.9%	3242	24.2%	6476	24.1%
Smoking	6982	51.6%	6851	51.2%	13833	51.4%
Family history	1226	9.1%	1157	8.6%	2383	8.9%
Diabetes	7350	54.3%	7286	54.5%	14636	54.4%
Dyslipidemia	8690	64.2%	8750	65.4%	17440	64.8%
Hypertension	10444	77.2%	10446	78.1%	20890	77.6%
COPD	2223	16.4%	2220	16.6%	4443	16.5%
Cerebrovascular disease	1610	11.9%	1583	11.8%	3193	11.9%
Renal insufficiency	4273	31.6%	5319	39.8%	9592	35.6%
Hemodialysis	1568	11.6%	1634	12.2%	3202	11.9%
Arrythmia (Af/AF)	518	3.8%	472	3.5%	990	3.7%
Extracardiac arteriopathy	2330	17.2%	2431	18.2%	4761	17.7%
Surgery on PAD/AAA	646	4.8%	523	3.9%	1169	4.3%
NYHA class III, IV	2654	19.6%	2805	21.0%	5459	20.3%
Old myocardial infarction	3179	23.5%	3086	23.1%	6265	23.3%
Acute myocardial infarction	1671	12.3%	1687	12.6%	3358	12.5%
Unstable angina	4506	33.3%	4616	34.5%	9122	33.9%
History of PCI	3301	24.4%	3245	24.3%	6546	24.3%
Stent thrombosis	250	1.8%	228	1.7%	478	1.8%
Indication for CABG in relation to PCI
PCI complication	165	1.2%	164	1.2%	329	1.2%
PCI failure w/o clinical deterioration	346	2.6%	410	3.1%	756	2.8%
PCI/CABG hybrid procedure	360	2.7%	300	2.2%	660	2.5%
Clinical other than above	267	2.0%	269	2.0%	536	2.0%

AAA: abdominal aortic aneurysm; Af/AF: atrial fibrillation/flutter; CABG: coronary artery bypass grafting; COPD: chronic obstructive pulmonary disease; NYHA: New York Heart Association; PAD: peripheral arterial disease; PCI: percutaneous coronary intervention.

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Table 2-1.

Graft selection for elective cases.

Age(years)	Overall	SITA						BITA						NoITA
		Total SITA	With SVG	Without SVG				Total BITA	With SVG	Without SVG
				no RA, no GEA	RA+GEA	RA no GEA	GEA no RA			no RA, no GEA	RA+GEA	RA no GEA	GEA no RA
n	22168	12991	10508	1440	133	587	323	8183	5453	1675	36	220	799	994
∼49	1149	548	348	90	16	58	36	560	326	109	6	31	88	41
		47.7%						48.7%						3.6%
50∼59	2574	1253	942	139	40	84	48	1234	827	202	8	55	142	87
		48.7%						47.9%						3.4%
60∼69	6863	3719	2997	380	49	198	95	2883	1910	577	13	73	310	261
		54.2%						42.0%						3.8%
70∼79	8853	5530	4636	559	25	195	115	2901	2004	615	7	52	223	422
		62.5%						32.8%						4.8%
80∼	2729	1941	1585	272	3	52	29	605	386	172	2	9	36	183
		71.1%						22.2%						6.7%

BITA: bilateral internal thoracic arteries; ITA: internal thoracic artery; GEA: gastroepiploic artery; RA: radial artery; SVG: saphenous vein graft; SITA: single internal thoracic artery.

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Table 2-2.

Graft selection for urgent/emergent/salvage cases.

Age(years)	Overall	SITA						BITA						NoITA
		Total SITA	With SVG	Without SVG				Total BITA	With SVG	Without SVG
				no RA, no GEA	RA+GEA	RA no GEA	GEA no RA			no RA, no GEA	RA+GEA	RA no GEA	GEA no RA
n	4745	3065	2647	227	2	134	55	1206	791	292	3	22	98	474
∼49	217	118	97	11	0	5	5	77	47	17	1	1	11	22
		54.4%						35.5%						10.1%
50∼59	455	249	196	23	0	23	7	171	110	39	1	5	16	35
		54.7%						37.6%						7.7%
60∼69	1280	797	686	61	2	34	15	396	254	98	1	5	38	87
		62.3%						30.9%						6.8%
70∼79	1822	1214	1064	81	0	50	18	432	296	97	0	11	28	176
		66.6%						23.7%						9.7%
80∼	971	687	604	51	0	22	10	130	84	41	0	0	5	154
		70.8%						13.4%						15.9%

BITA: bilateral internal thoracic arteries; GEA: gastroepiploic artery; RA: radial artery; SVG: saphenous vein graft; SITA: single internal thoracic artery.

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Table 3.

Graft selection for LAD revascularization.

	LITA-LAD	RITA-LAD	RA-LAD	GEA-LAD	SVG-LAD
Total	20108	4997	103	13	1098
	76.4%	19.0%	0.4%	0.0%	4.2%
Age (years)
∼49	995	282	10	3	31
	75.3%	21.3%	0.8%	0.2%	2.3%
50∼59	2213	649	11	2	81
	74.9%	22.0%	0.4%	0.1%	2.7%
60∼69	6015	1678	30	2	242
	75.5%	21.1%	0.4%	0.0%	3.0%
70∼79	8020	1938	36	5	432
	76.9%	18.6%	0.3%	0.0%	4.1%
80∼	2865	450	16	1	312
	78.6%	12.3%	0.4%	0.0%	8.6%

LAD: left anterior descending artery; LITA: left internal thoracic artery; GEA: gastroepiploic artery; RA: radial artery; SVG: saphenous vein graft.

Operative death and immediate postoperative morbidity rates are presented in Table 4. Furthermore, comparative data between OPCAB and on-pump CABG are presented. OPCAB was performed in 54.6% of all isolated CABG cases (n = 14,684), and the case volume was stable from the previous two reports. In the overall cohort, the incidence of operative death was found to be 2.5% (3.0% in the previous report); reexploration for bleeding occurred in 1.0% of cases, with a slight decrease from the previous report (1.7%); and new-onset atrial fibrillation (AF) decreased to 10.9% of cases (12.4% in the previous report). There was an increase in readmission rates within 30 days after discharge from 0.5% to 2.1%. In elective cases, OPCAB showed lower rates of operative mortality and morbidity, except for gastrointestinal complications, than on-pump CABG cases. For urgent, emergency, and salvage cases, major morbidities were lower, except for new-onset AF and readmission, and operative death was also better with OPCAB than with on-pump CABG (4.3% vs. 7.4%, p < 0.001). Table 5 shows operative mortality by age. A gradual increase according to age was clearly observed. Table 6 summarizes the annual trend of expected mortality using JapanSCORE II since 2013. An increase in JapanSCORE II was observed by year, which suggests an increase in the preoperative risk status of patients.

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Table 4.

Perioperative results.

	Overall		Elective							Urgent/emergency/salvage
	26913		ONCAB		OPCAB		Total		p value (ONCAB vs OPCAB)	ONCAB		OPCAB		Total		p value ONCAB vs OPCAB)
No. of patients	(OPCAB: 14684, 54.6%)		9715(43.9%)		12453(55.1%)		22168(100%)			2514(53.0%)		2231(47.0%)		4745(100%)
Operative death	683	2.5%	180	1.9%	151	1.2%	331	1.5%	<0.001	257	10.2%	95	4.3%	352	7.4%	<0.001
Bleeding	267	1.0%	120	1.2%	87	0.7%	207	0.9%	<0.001	46	1.8%	14	0.6%	60	1.3%	<0.001
Stroke	463	1.7%	156	1.6%	137	1.1%	293	1.3%	0.001	121	4.8%	49	2.2%	170	3.6%	<0.001
Deep sternal infection	454	1.7%	189	1.9%	160	1.3%	349	1.6%	<0.001	67	2.7%	38	1.7%	105	2.2%	0.02
Prolonged ventilation	936	3.5%	265	2.7%	217	1.7%	482	2.2%	<0.001	309	12.3%	145	6.5%	454	9.6%	<0.001
Pneumonia	317	2.4%	95	2.0%	95	1.5%	190	1.7%	0.051	85	6.6%	42	3.9%	127	5.4%	<0.001
Renal failure	987	3.7%	320	3.3%	264	2.1%	584	2.6%	<0.001	275	10.9%	128	5.7%	403	8.5%	<0.001
AF	2937	10.9%	1074	11.1%	1270	10.2%	2344	10.6%	0.04	325	12.9%	268	12.0%	593	12.5%	0.34
GI complication	322	1.2%	93	1.0%	122	1.0%	215	1.0%	0.89	73	2.9%	34	1.5%	107	2.3%	0.001
Readmission<30 days	578	2.1%	207	2.1%	284	2.3%	491	2.2%	0.45	43	1.7%	44	2.0%	87	1.8%	0.5

AF: atrial fibrillation; GI: gastrointestinal; ONCAB: on-pump coronary artery bypass; OPCAB: off-pump coronary artery bypass.

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Table 5.

Mortality according to age.

	Elective			Urgent/emergency/salvage
	Total	No. of deaths	%	Total	No. of deaths	%
	22168	331	1.5%	4745	352	7.4%
Age (years)
∼49	1149	8	0.7%	217	10	4.6%
50∼59	2574	25	1.0%	455	20	4.4%
60∼69	6863	79	1.2%	1280	68	5.3%
70∼79	8853	160	1.8%	1822	150	8.2%
80∼	2729	59	2.2%	971	104	10.7%

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Table 6.

JapanSCORE II 30-day mortality: yearly trend.

Year	2013	2014	2015	2016	2017	2018
No. of patients	14416	13900	13759	13220	13429	13328
p5	0.3	0.3	0.3	0.3	0.3	0.4
p25	0.6	0.6	0.6	0.6	0.7	0.8
median	1.1	1.2	1.2	1.3	1.3	1.6
p75	2.5	2.7	2.8	2.9	3.2	3.6
p95	11.0	12.1	12.1	12.1	13.2	14.0

Discussion

The Committee of the Society of Thoracic Surgeons (STS) National Database updated their clinical results in 2018 with regards to isolated CABG procedures performed in 2016. The overall in-hospital and operative mortalities were reported to be 1.7% and 2.2%, respectively, which were similar to the results in 2015.^3,4 On the other hand, our results showed that overall operative death was 2.5% in 2017 and 2018 which is fairly consistent with the recent STS report. ⁴ Operative mortality usually exceeded in-hospital mortality in the STS annual reports, and this phenomenon would not occur in Japan because the duration of hospital stay is generally longer and in-hospital mortality covers 30-day operative mortality in general. Notable results from our analysis were a higher mediastinitis rate (1.7%) and a lower incidence of new-onset AF (10.9%) than the STS report (0.3% for mediastinitis and 24.9% for AF). Rates of AF were similar in on-pump and off-pump CABG; thus, commitment cardiopulmonary use may be unnecessary. Possible causes for this observation remain unclear. The frequency of BITA use did not change, and the distribution of RA use was noted with an increase in elective cases in combination with SITA and a remarkable decrease in combination with BITA. Detailed investigation of RA use (e.g., proximal anastomosis to the ascending aorta or ITA) may provide clues to this trend in the frequency of RA use. GEA use slightly decreased in the SITA group; however, it was similar to that reported in the previous report in the BITA group, suggesting a stable preference for in-situ arterial grafting, including GEA, to achieve the ‘aorta no-touch’ technique.

Postoperative complications occurred more often in on-pump CABG than in OPCAB, in general, with the exception of similar occurrences of gastrointestinal complications, readmission, and pneumonia. The dominance of OPCAB in isolated CABG has been declining slightly after 10 years of stable use, with 58.8% in 2017 in the recent Japanese Association for Thoracic Surgery annual report. ⁵ In our recent study based on the JCVSD, the OPCAB rate was 54.6%, which is similar to the 55.0% reported previously. ² A new attempt in this report was to present JapanSCORE II for operative mortality, which indicates risk stratification for those undergoing isolated CABG. The results imply gradual worsening of the patients’ risk profiles, which explains the requirement for cardiopulmonary bypass use to achieve a satisfactory degree of coronary revascularization.

Nawata and colleagues ⁶ published interesting data comparing short-term surgical results of isolated CABG between an Asian cohort from the STS Adult Cardiac Surgery Database (STS-ACSD) and those from the JCVSD. For the JCVSD cohort, patients’ age at operation, body surface areas, and comorbidities of hypertension and dyslipidemia were low, and history of smoking and renal replacement therapy were frequently found. On the other hand, surgery after myocardial infarction was more frequently performed in the STS-ACSD cohort. Perioperative results showed that operative death and transfusion rates were high in the JCVSD cohort, whereas new-onset AF and postoperative ventilation exceeding 24 hours were high in the STS-ACSD cohort. This study presents a simple description of the raw data and not a comparative study with risk adjustment; thus, definitive conclusions cannot be obtained. However, this study still provides interesting data showing that patients of the same race may present different preoperative characteristics depending on the place of residence, implying the importance of national clinical databases such as the JCVSD and STS-ACSD.

In summary, short-term clinical outcomes of isolated CABG procedures in 2017 and 2018 were analyzed based on data registered in the JCVSD, a nationwide clinical database. Some changes in RA use were found compared to previous reports. OPCAB provided favorable operative results, including operative death and major morbidities, and operative death for on-pump CABG also improved from the previous report.