Does transesophageal echocardiography improve postoperative outcome in patients undergoing coronary artery bypass surgery?

Does Transesophageal Echocardiography Improve Postoperative Outcome in Patients Undergoing Coronary Artery Bypass Surgery? Michihisa

Kato, MD, Yasushi Nakashima,

MD, Jeffrey Levine, MD, Paul L. Goldiner,

The incidence and characteristics of ischemic episodes as detected by transesophageal echocardiography (TEE) and their relationship to postoperative myocardial infarction (MI) and adverse clinical outcome were studied in patients undergoing coronary artery bypass grafting (CABG). Seventeen of 50 patients had 21 TEE-defined ischemic episodes: 4 patients (8%) had 4 ischemic episodes in the pre-cardiopulmonary bypass (CPB) period, and 15 patients (30%) had 17 ischemic episodes in the post-CPB period, whereas 19 patients had 20 ECG ischemic episodes: 3 patients (6%) had 3 ischemic episodes in the pre-CPB period and 17 (34%) had 17 ischemic episodes in the post-CPB period. In 14 patients, ischemic episodes were detected by both TEE and ECG. Clinicians were made aware of the TEE data and appropriate treatments were undertaken during ischemic episodes: of the 15 patients with TEE-defined post-CPB ischemia, 4 had an additional saphenous vein graft placed, 8 had an intra-aortic balloon pump (IABP) inserted, 3 were given sublingual ni-

I

T IS WIDELY accepted that intraoperative myocardial &hernia is associated with a high incidence of postoperative MI in patients undergoing CABG.1~2 Using the more sensitive modality of intraoperative TEE, myocardial ischemia can be detected as RWMA during surgery. Smith et al3 demonstrated that RWMA were associated with postoperative MI in patients undergoing CABG and vascular surgery. Additionally, Leung et al4 reported that the incidence of myocardial ischemia was higher in the post-CPB period than pre-CPB, and intraoperative myocardial ischemia was associated with adverse outcome. However, London et al5 reported that intraoperative ischemia as defined by RWMA correlated poorly with postoperative cardiac complications in patients undergoing vascular surgery. Thus, the relationship between TEE-defined ischemia and postoperative cardiac complications remains controversial. This study was designed to evaluate the incidence and characteristics of myocardial ischemia as detected by TEE and its relationship to postoperative MI and adverse clinical outcome in patients undergoing CABG. METHODS Fifty-six patients scheduled for elective CABG were enrolled in this study. Patients with esophageal or gastric disease and patients undergoing combined CABG and valvular surgery were excluded. This study was approved by the institutional research committee and informed consent was obtained from each patient. Preoperative clinical data included a history of MI, previous CABG, hypertension, diabetes mellitus, congestive heart failure, and the number of significant coronary artery stenoses ( 2 70% stenosis of the left anterior descending, left circumflex, or right coronary artery, and 250% stenosis of the left main coronary artery). Anesthesia was induced and maintained with sufentanil (mean dose of 25 kg/kg) and diazepam (0.4 mgikg), and muscle relaxation was obtained with vecuronium or pancuronium. Isoflurane was added if necessary to control blood pressure. Cardiopulmonary bypass (CPB) was performed with membrane oxygenators (Maxima, Medtronic, Anaheim, CA) under total body hypothermia (3o”C), and antegrade intermittent cold blood cardioplegia with potassium (initial dose: 28-30 mEq/L, maintenance dose: 10 to 14

Journalof

Cardiothoracic

and

VascularAnesthesia,

Vol

7, No 3

MD, and Yasu Oka, MD

fedipine, and 13 received nitroglycerin. These treatments resulted in improvement in regional wall motion abnormalities (RWMA) by the end of surgery in 11 of the 15 patients (73%). including the 4 with postoperative Ml and 2 who died with cardiogenic shock. The authors conclude that: (1) significantly more patients had TEE-defined ischemic episodes in the post-CPB period (30%) than in the pre-CPB period (8%); (2) a poor graft and/or inadequate myocardial protection were strongly suggestive of post-CPB ischemia, which was significantly related to adverse outcome; and (3) TEE was a useful tool enabling detection of problem areas at an early stage and timely and appropriate treatment to support and sustain patients. CopYright 0 1993 by W.B. Saunders Company KEY WORDS: myocardialischemia, transesophagealechocardiogrephv, postoperative outcome

mEq/L) except in 8 patients who received both antegrade and retrograde cardioplegia. After intubation, a ~-MHZ phased-array transesophageal echocardiographic probe (PEF-SllSA, Toshiba, Japan) was inserted and connected to an echocardiographic system (SSH-140A, Toshiba, Japan). The probe was positioned to obtain a short-axis view of the left ventricle (LV) at the mid-papillary muscle level. The TEE was continuously monitored except during CPB. Images were recorded on VHS video tape every 15 minutes, soon after tracheal intubation, and 1 minute after skin incision, sternotomy, pericardiotomy, aortic cannulation, and sternal closure. The probe was removed at the end of surgery. The short-axis view at the mid-papillary muscle level was divided into eight segments according to the nomenclature recommended by the American Society of Echocardiography (Fig 1). The wall motion of each of the segments was graded as follows: 0 = normal, 1 = mild hypokinesia, 2 = severe hypokinesia, 3 = akinesia, and 4 = dyskinesia. RWMA score was calculated as the sum of the gradings of all 8 LV segments. The estimates of endocardial excursion and myocardial thickening were made visually (Table 1). The wall motion in each segment soon after tracheal intubation was used for the baseline value for each segment. An ischemic episode was defined as a worsening in wall motion of any segment by two or more grades from the baseline. The surgeons and anesthesiologists were made aware of the TEE data during surgery. When the TEE operator (MK) detected a RWMA, treatment was instituted according to the decisions of the surgical team. An improvement of wall motion was defined as a return to the baseline or within one grade. The TEE data were subsequently analyzed by two independent observers (MK and YN) viewing the videotaped data after surgery. The accuracy of their ischemia detection was defined as the percentage of segments with identical scores and its concordance as the percentage of segments with a variation of one grade in scoring. All TEE data were re-examined six months later by one observer (MK).

From Albert Einstein College of MedicinelMontefiore Medical Center, Department of .rlnesthesiology, Bronx, NY. Address reprint requests to Yasu Oka, MD, Department of Anesthesiology (F-726 S), Albert Einstein College of Medicine, 1300 Morris Park Ave, Bronx, NY 10461. Copyright o 1993 by W.B. Saunders Company 1053-0770/9310703--0006$03.00/0

(June), 1993: pp 285-289

285

INFERIOR

INFERIOR LVFW ,’ ’ INFERO-

\

tient\ at-c presciitcd ranging

’ ANTERIOR LVFW

ANTERIOR RVFW / ’ -1 LAD

LCX

v/j Lo

RCA

Fig 1. Schematic diagram of short-axis view of left ventricle at mid-papillary muscle level using the nomenclature recommended by the American Society of Echocardiography. LVFW, left ventricular free wall; RVFW, right ventricular free wall; VS. ventricular septum.

Electrocardiography (ECG: V&ad) and routine hemodynamic measurements including heart rate (HR), systolic. diastolic, and mean arterial pressures (SAP, DAP, MAP), pulmonary artery diastolic pressure (PADP), and cardiac output (CO) were obtained prior to induction of anesthesia and simultaneously with each TEE examination point. The pressure-rate quotient (PRQ) was defined as the MAP divided by HR. Ischemic episodes detected by ECG were defined as an ST segment shift from baseline of r0.1 mV depression or 20.2 mV elevation at J + 60 msec. Hemodynamic variables were compared between the pre-CPB and post-CPB periods in all 50 patients, as well as between ischemic and non-ischemic periods post-CPB. Twelve-lead ECG and serum CPK levels with MB isoenzyme fractions were obtained from postoperative day 0 to day 7. Postoperative MI was diagnosed by new Q waves on the ECG, serum CPK level 2 700 U/L, and CPK-MB z 7% of total CPK.

Postoperative echocardiography to look for new persistent RWMA was not performed. Hemodynamic variables, CPK, and age are presented as the mean + one standard deviation and were tested by an unpaired f-test. x2 Test with Yates correction or Fisher’s exact test was used to test categorical data. P < 0.05 was considered significant. RESULTS Incidence

qf‘Ischemic Episodes

Six patients out of the 56 enrolled in the study were excluded due to inability to obtain adequate short-axis views of the LV. Twenty-seven men and 23 women were studied. The clinical and demographic data of these paTable 1. Criteria for Oualitative Scoring of Regional Wall Motion Abnormality

Grade

Endocardtal

Wall

Excursion

Thlckening

+++

Normal Hypokinesis Mild

Reduced

Severe

Reduced

++ +

Akinesis

Absent

Absent

Dyskinesis

Outward bulging

Systolic thinning

111Tablt: I: A lotal of041 TEI: i;impii,.

7 to 71 (mcun

12.X + 3.0)

per

patient

wet-c

samples exhihlteli RWMA. this was considcrcd a single ischemic episode Scvcnteen of’ SO patients (34’::) had a total of 21 TEF defined ischcmic episodes during CABG. The distribution of TEE ischemic episodes was 3 of 21 cpisodcs (19?) in the pre-CPB period and 17 ~jt 2 I cpisodcs (Xl% ) In 111~ post-CPB period. The difference was statistically significant (P < 0.01). RWMA occurred most commonly (22%) in the inferior left ventricular free wall (Fig 2). Thcrc was no difference in all of the preoperative clinical data except for age bctwccn those patients who had TEE ischemic cpisodc\ and those who did not. The mean age way signiticantiy lower (P < 0.05) in patients with TEE ischemia. Postopcr:ltivc C’PK-MB isocnzymc levels wcrc significantly higher (P < 0.05) in patients with ischemic cpisodcs. Inrraohserver accuracy was X7% and its concordance with [he XXIIobservation 6 months later was 99%. Intcrohscrvcr racy was X1?S with ;I concordance of 9X’;:. The incidence ot 3 ECG ischcmic cpisodcs was 20 cpisodcs in I9 patients patients (6%)) had 3 ischemic cpisodcs in the prc-CPB period and 17 (34’;) had I? ischcmic episodes in the post-CPB period. Both TEE- and ECG-defined myocardial ischemia was dctccted in only one patient pre-C’PB and ill 13post-CPB. analyLcd.

MIDDLE RVFW

from

If two

Postoperutive

or

Curd&

more

i’onsccutive

Cornplic~utior~s

Six of the 15 patients (40%) had postopcrativc complicutions (Table 3). One patient (no. 8) died of ventricular arrhythmias. with TEE-defined and ECG-defined ischemia in the pre-CPB and post-CPB period, cardiogenic shock. and multiple organ system failure for 7 days postoperation. Another patient (no. 49) suddenly died of fatal ventricular tachycardia on postoperative day 3. There was no elevation in the CPK-MB levels in these 2 patients: however. in patient no. 49, the sequential graft to the first diagonal and left anterior descending arteries was noted to be thronboscd at the time of resuscitation. The remaining four patients (nos. 26. 31. 45, 46) were diagnosed as having suffcrcd postoperative MIS and had ischcmic episodes onI> in the post-CPB period detected by both TEE and ECG. In 3 of these 4 patients with postoperative MI. the areas ot intraoperative RWMA corresponded to the areas of ECGdiagnosed postoperative MI. The remaining 9 patients with TEE ischemic episodes in the post-CPB period did not suffer postopcrativc cardiac complications. The ischcmic episodes detected by both TEE and ECG in the post-CPB period were significantly (P < 0.001, P < 0.001) associated with adverse outcome (Table 4). Treatment

In 3 of the 15 patients with post-CPB TEE &hernia, the left internal mammary artery graft to the left anterior descending artery was considered to be of poor quality and a saphenous vein graft was added. In one patient (no. 45), a vein graft was added to the right coronary artcry. An intra-aortic balloon pump was inserted in 8 patients.

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Table 3. Postoperative Cardiac Complications and lntraoperative

_._-___-

lschemlc

1

(~-

Patient

PR-

Post-

NO

CPB

CPB

rredtments NTG

NIT

IABP

Graft

Graft

MS, AS

(t)

NTG

IABP

49

IP, PL, AL, A

(+/

NTG

IABP

26

IP, PL, AL

(1)

NTG

IABP

31

I, IP

i+ i

NTG

45

l/l

ii)

IP, PL

IfI

NTG

AS

(- 1

NTG

I, IS, MS

( t)

46 2 6 15

AS

0

PL, AL

/-j

MS

NTG

IABP IABP

(t-1

NTG

(4

)

NTG

j-j (+j I (+1 ( b)

NTG

AS, MS

(+I

NTG

I, lP/l

(+I

NTG

I

41

AS, MS, IS,

43

I

48

(+)

50 *Died of ventricular tDied

thrombosed. *Added

Thrombectomy

saphenous

NTG, nitroglycerin;

vein graft; I, inferior

IABP

6

graft to the first diagonal

and left anterior

descending

artery

noted to be

was not successful.

artery. Nif, nifedipine;

IABP, intra-aortic

balloon

pump;

free wall (LVFW); IP, inferoposterior

Graft, left internal

LVFW; PL, posterolateral

mammary

artery

was changed

LVFW; AL, anterolateral

to a

LVFW; A,

septum (KS), MS, middle VS; IS, inferior VS.

ECG

TEE

1

2

6

6

3

1

9

11

P

i

0.001

technique, and needed an additional graft as well as the IABP; no. 49 had normal LV function before CPB. but needed an IABP following CPB, and died on postoperative day no. 3 with thrombosed grafts. Four patients had postoperative MIS (nos. 26, 31, 45 and 46). Patients nos. 26. 31, and 46 had good LV function, normal TEES and ECG pre-CPB, but had TEE and ECG evidence of ischemia post-CPB. They needed additional vein grafts in patients 26 and 45 and IABP in patients 26, 31, 46. However, their postoperative courses were smooth. These lindings strongly indicated that post-CPB ischemia is related to poor quality of grafts and/or inadequate myocardial protection. In 3 patients, RWMA did not improve, but they did not suffer an adverse outcome. Reasons for this arc not clear, but ail 4 patients had a documented preoperative Ml. London et al’ did not find good correlation between intraoperativc Table 5. Hemodynamic Variables in all 50 Cases Pre-CPB

HR (beatsimin)

ECG

P

<

0.001

(n = 3311

post-CPB

69.8 t 14.6

(il

310!

91.01151’

SAP (mmHg)

115.9 2 18.9

DAP (mmHg)

60.8 I? 10.5

55.2 + 9.5*

MAP (mmHg)

79.3 +- 13.2

73.2 t 11.2*

PAD/LAP

10.6 + 4.1

13.3 I 4.8X

1.18 z!z0.28

0.83 r 0.19”

(mmHg)

PRQ

Post-CPB

NS

LBBB

at bedside, but resuscitation

TEE

NS

lnferolateral

shock, sepsis, and acute renal failure on POD #7.

Pre-CPB

t-144

1554:15

V. Pacing

$

lschemic Changes and Adverse Clinical Outcome

I+)

Anterolaterai

+ +

IABP

Table 4. The Relationship Between Patients With lntraoperative

Outcome

i

Graft

of 1X patients with post-CPB ischemia detected by TEE had adverse outcome whereas none of the 32 patients without TEE ischemia had an adverse outcome. However, in a study of 156 high-risk patients undergoing non-cardiac surgery, London et al5 used both continuous short-axis views of the left ventricle and 12-lead ECG to study the incidence of intraoperative ischemia and its relation to outcome. They found a 20% incidence of new or worsened RWMA, but these were poor correlates of postoperative cardiac complications. In the present study, post-CPB TEE ischemia as well as post-CPB ECG ischemia was significantly associated with adverse outcome. Patients with RWMAs identified intraoperatively reccived treatments such as nitroglycerin and/or nifedipine, IABP insertion, and additional vein grafts according to the decisions of the attending surgeon and anesthesiologist. These treatments resulted in improvement of RWMA in 11 of 15 patients with post-CPB ischemia. In those 11 patients, 2 patients (nos. 8, 49) died with cardiac death; no. 8 had poor left ventricular function and RWMAs before CPB and had prolonged surgery because of difficulty in surgical

Adverse

lnferlor

764:9

NTG

left ventricular

LVFW; AS, anterior ventricular

NIF

on POD #3. His sequential

was performed

Anterolaterai

NTG

cardiogenic

tachycardia

a vein graft to right coronary

Abbreviations: anterior

arrhythmia,

of fatal ventricular

I134:ZO 1 100:7

IABP

NTG

AL, A

i ~1

I

Graft

NIF

l--l

AL, A. AS A, AS

/*

/

IABP

(+I

19

34

NIF

i

Graft*

25 28

lschemic Episodes

Episodes

TEEiECG

8

I i

104.0 i

17.9x

NOTE. Values are mean t SD. *P i 0.001. Abbreviations: mean arterial atrial pressure;

HR. heart rate; SAP, DAP, MAP, systolic, pressure;

PAD/LAP,

PRO, pressure-rate

pulmonary quotient.

artery

diastolic,

diastolic

or left

289

TEE EVALUATION OF MYOCARDIAL ISCHEMIA

Table 6. Hemodynamic Variables in the Post-CPB Period Nonischemic Period (n = 261)

lschemic Period (n = 49)

89.0 + 13.5

101.9 2 18.3”

SAP (mmlig)

106.0 + 16.5

93.7 2 21.6*

DAP (mmHg)

56.0 + 8.8

51.2 + 12.0”

MAP (mmHg)

74.1 + 10.4

68.6 + 14.2t

HR (beatsimin)

PAD/LAP

(mmHg)

PRQ

12.9 k 4.2

15.1 f 7.0t

0.85 2 0.18

0.70 -t 0.22*

4.8 + 1.4

CO (L/min)*

4.6 + 1.3 NS

NOTE. Values are mean + SD. ?? P < 0.001.

tP < 0.005. Sn = 72 in nonischemic, Abbreviations: mean arterial atrial pressure;

n = 19 in ischemic period.

HR, heart rate; SAP, DAP, MAP, systolic, pressure;

PAD/LAP,

PRQ, pressure-rate

pulmonary quotient;

artery

diastolic,

diastolic

or left

CO, cardiac output.

RWMA and postoperative cardiac complications in noncardiac surgical patients. Causes of RWMAs in noncardiac surgical patients must differ from that of cardiac surgical patients. The following points should be emphasized:’ the short-axis view of the left ventricle at the mid-papillary muscle level was used in detecting RWMA. Shah et al’” reported that when using biplane TEE, RWMA were detected only in the basal and apical regions in 35% of patients with ischemia, and they stated that those could have been missed when only the mid-papillary muscle level was used. However, both of those regions were scanned

whenever a RWMA was found in the mid-papillary muscle level, and in 3 of 4 patients with a postoperative MI, it was noted in the same area as the RWMA detected post-CPB; and alterations in loading conditions and contractile state may affect the assessment of wall motion.r4 Ross15 suggested that altered loading conditions can change the degree of regional dysfunction due to acute ischemia or chronic scar formation without necessarily affecting the degree of ongoing ischemia. Kerber et alI6 reported that positive inotropic agents improve both the velocity of motion and wall excursion of acutely ischemic myocardium. Thus, the use of pharmacologic and mechanical support could have affected regional wall motion, masking an ongoing ischemic process in the 6 patients with adverse outcomes. Leung et al4 reported that 11 of 18 patients (61%) with postbypass myocardial ischemia suffered an MI in the ICU period. The present study was not able to demonstrate whether some of the patients had further ischemic episodes in the ICU or not. It is concluded that (1) TEE ischemic episodes occur more frequently in the post-CPB period (81%) than in the pre-CPB period (19%); (2) poor graft flow and/or inadequate myocardial protection were strongly suggestive of post-CPB ischemia and significantly related to adverse outcome; and (3) the majority of RWMA responded to intraoperative treatments. The TEE was useful for detecting ischemic changes in specific areas of the ventricle and for instituting timely treatment.

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myocardial &hernia lead to postoperative myocardial infarction? Anesthesiology 62:107-

between regional myocardial dysfunction and ECG changes during ischemia in the conscious dog. Circulation 62:735-744, 1980

114,1985

10. Hauser AM, Gangadgaran V, Ramos RG, et al: Sequence of mechanical, electrocardiographic and clinical effects of repeated coronary artery occlusion in human beings: Echocardiographic observation during coronary angioplasty. J Am Co11 Cardiol 5:193197,1985

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