Right Ventricular
Function in Patients With Reduced Left Ventricular Undergoing Myocardial Revascularization
Function
Joachim Boldt, MD, Bernfried Zickmann, MD, Christoph Herold, Friedhelm Dapper, MD, and Gunter Hempelmann, Complex interrelationships exist between the right (RV) and the left ventricles (LV). Therefore, in 30 consecutive patients with reduced LV function (left ventricular ejection fraction [LVEF]) ~40% undergoing myocardial revascularization, RV hemodynamics were studied from the beginning of anesthesia until the end of the operation. The data were compared with 30 consecutive patients with normal LVEF (> 70%). Ventricular function was assessed during left heart catheterization, which was carried out within 1 month of the operation. In addition to standard hemodynamic variables, RV ejection fraction (RVEF), RV end-diastolic volume (RVEDV), and RV end-systolic volume (RVESV) were monitored by the thermodilution technique. The two groups did not differ preoperatively with regard to RVEF, pressure (MAP, PAP,
I
MPROVEMENTS in surgical technique, extracorporeal oxygenation, myocardial protection during cardiopulmonary bypass (CPB), and perioperative anesthetic management have led to improved results in patients with reduced the outcome in these myocardial function.’ 4 However, patients with markedly impaired left ventricular function [left ventricular ejection fraction (LVEF) < 40%] undergoing myocardial revascularization is still not as good as in patients with good myocardial performance.’ The left ventricle (LV) is perceived as the cardiac structure of greatest importance for pump function, and the role of the right ventricle (RV) has been questioned.‘.h However, inadequate overall cardiac performance secondary to RV dysfunction, caused by overload or ischemia, has become more and more apparent in recent studies.“’ Moreover, the RV and the LV are in series and mechanically coupled so that a disturbance in the mechanical function
of one ventricle
other.‘4-‘b of
the
Thus, right
undergoing
investigate alterations
there side
of
will influence
is growing the
heart,
interest
the behavior
of the
in the importance
particularly
in
patients
surgery.” This study was performed to whether reduced LV function is associated with in RV function. cardiac
MATERIALS
AND METHODS
Sixty patients undergoing elective myocardial revascularization were investigated after the study protocol was approved by the Institutional Ethics Board and informed consent was obtained. The patients were divided into 2 groups based on their LVEF obtained by left heart catheterization within 1 month of the operation: Group 1: 30 consecutive patients with a LVEF 70% (normal LV function). Exclusion criteria from the study were metabolic disorders, concomitant valvular diseases, unstable angina. pulmonary hypertension, and acute right heart failure. Premeditation with morphine, 0.15 mgikg, and flunitrazepam. 0.02 mgikg, was given I.5 hours before entering the operating room. Induction of anesthesia consisted of intravenous administration of fentanyl, 5 kg/kg. midazolam, 0.15 mg/kg, and pancuronium bromide, 0.1 mgikg. All patients were placed on mechanical ventilation with an F,O, of 1.0 and zero end-expiratory pressure. For maintenance of anesthesia, fentanyl (total dose: 35 Kg/kg). midazolam (total dose: 0.70 mgikg). and pancuronium bromide (total dose: 0.2X mgikg) were used. During and after CPB. midazolam (5 mg) and pancuronium hromide (2 mg) were given every 30 minutes. The total dosage of anesthetics was comparable for both groups. CPB was carried out using a membrane oxygenator (Sorin 41. Fa. Sorin, Torino. Italy) after 300 IU/kg of heparin were given to achieve anticoagulation. The extracorporeal circuit was primed with a mixture of 2,000 mL of crystalloids and 250 mL of 54 albumin. A monoatrial cannulation technique was used for drainage of the venous blood. The patients were kept nearly normothermic (lowest rectal temperature: 33.8 f 0.4”C) and a flow of 2.4 L/minim’ was maintained during the entire period of CPB. Ice cold Bretschneider’s cardioplegic solution was infused for myocardial protection. All patients were operated on by the same surgical team. During and after weaning from CPB, positive inotropic supper-t (calcium, epinephrine) was given when mean arterial pressure (MAP) was below 60 mm Hg or when cardiac index (CI) was les< than 2.0 L/minim’. Vasodilators (nitroglycerin) were administered when the pulmonary capillary wedge pressure (PCWP) was more than 20 mm Hg or systemic vascular resistance (SVR) was more than 1600 dyne s cm-‘. Volume (low molecular weight hydroxy ethyl starch solution) was infused to guarantee sufficient tilling (PCWP > 8 mm Hg). Volume administration and all pharmacological support were decided on hy an anesthesiologist not involved in the study. Hemodynamic monitoring consisted of measuring heart rate (HR), MAP, pulmonary artery pressure (PAP). right atrial pressure (RAP). and cardiac output (CO, thermodilution technique). Derived cardiovascular variables (SVR and CI) were calculated from standard formulae. The pulmonary artery catheter, inserted
Journalof Cardiothoraoc and VascularAnesthesra, Vol 6, No 1 (February), 1992: pp 24.28
RV FUNCTION
via the right jugular vein, was specifically designed to additionally measure right ventricular ejection fraction (RVEF), right ventricular end-systolic volume (RVESV), and right ventricular enddiastolic volume (RVEDV) using a thermodilution technique and a microprocessor (model REF-1; Edwards Laboratory, St Ana, CA). Normal values of RVEF assessed by this method ranged from 40% to 50%. Theoretical background material and the detailed technique have been described elsewhere.‘S-20 All measurements based on the thermodilution principle were performed at endexpiration in triplicate, and the mean values were used for statistical interpretation. Hemodynamic measurements were performed after induction of anesthesia in a hemodynamic steady state (baseline value), after sternotomy, before the start of CPB (pericardium open), immediately after weaning from CPB (pericardium open), and at the end of the operation (50 minutes after CPB). All results are expressed as mean (X) 2 standard deviation (SD). The data were analyzed using one-way and two-way analyses of variance with replication. Analysis of covariance was used to detect a relationship between two variables. P values < 0.05 were considered statistically significant.
IRVEF(%)] 3
,/I,, I,,,, ,,,,, ,,,,, ,,,,, /,,,_, ,,jl/ 1,,1,1 ,I,,, ,/,,,_
A
rr;;;g
T
C
I
I
P B
I
1 !
ii?EEE
ifSD
after
induction
50
1
atter
SternOtomY
after
Pericardiotomy
50
1RVEF(%)1
45
45
1
RESULTS
Demographic data and data from CPB are listed in Table 1. LVEF was 32.4 2 5.4% in group 1 and 77.4 2 4.7% in Group 1 was subdivided into group 1A group 2 (control). with moderately depressed LV function (LVEF, 30% to 40%) and group 1B with severely depressed LV function (LVEF, 70%
15.8 2 3.2
14.2 -t 3.0
14.5 2 2.6
16.8 2 2.4
16.8 2 3.1
< 40%
10.2 ?I 4.3
9.1 * 4.0
8.3 2 2.2
10.3 f 2.6
11.1 2 2.9
> 70%
7.6 2 2.0
7.9 + 2.1
7.5 2 2.0
8.9 + 2.0
9.8 + 1.9
70%
3.02 f 0.38
3.00 + 0.33
3.03 + 0.30
2.70 + 0.32
2.72 + 0.30
70%
1066 + 110
1064 + 129
1022 + 166
1100 f 200
1244 k 222
NOTE. x + SD.
might be responsible for the increased RV afterload. Thus, it is likely that the pulmonary circulation is affected by the same humoral factors that elevate systemic resistance. Finally, because of relatively poorer RV preservation during CPB,” postoperative RV function may be impaired by ischemic myocardial areas. Thus, because ischemia of the RV myocardium seems to be the limiting factor in the response to a pressure load, previously reduced RV function may produce serious deteriorations in RV performance during and after weaning from bypass. In this study, RVEF was monitored perioperatively because it is the method most frequently used to describe systolic function of the RV.16 It is influenced by contractility, afterload, HR, and, to some extent, by preload.9,13 When patients with normal LVEF and reduced LVEF ( 30%. Ventricular volumes (RVEDV, RVESV) were always elevated, whereas pressure monitoring (RAP, RVPsyst, RVEDP) did not allow correct evaluation of ventricular function, demonstrating that pressure variables often are not sensitive enough to assess reduced RV function. RV decompensation may not be associated with a low RV diastolic pressure because of the high compliance characteristics of this chamber.32 Other advantages of using the thermodilution technique are that moni-
toring of RVEF, RVEDV, and RVESV is unaffected by arbitrary and poorly reproducible zero-points for pressure transducers, and the technique can be used serially at the bedside or in the operating room. Knowledge of RV function in patients with reduced LV function seems to be crucial because the treatment of dysfunction of either the RV or the LV may differ widely.“’ More catecholamines and volume were necessary during and after termination of CPB in patients with severely reduced LVEF. The RV as well as the LV may have benefited from the positive inotropic support; none of the patients suffered from critical right heart failure. However, a distinction must be made between RV dysfunction and RV failure. In patients with additional increased impedance of the pulmonary circulation (interstitial edema, microembolism, massive release of vasoactive substances), right heart failure will occur earlier in patients with a severely reduced LVEF. It is concluded that a better understanding of the perioperative role of the RV in disease states that primarily affect the LV is necessary. LV abnormalities might influence RV function, depending on the degree of its effect on diastolic volume, systolic function, or RV afterload by passive elevation of PAP. This study demonstrated that a reduced LVEF does not limit RV function over a wide range. However, a LVEF of 70%
24.7 ? 3.6
24.1 2 4.5
26.2 + 6.3
28.3 + 6.6
30.0 + 5.2
< 40%
27.2 2 8.8
29.3 f 6.3
31.3 r 7.3
32.1 r 7.7
33.3 + 7.6
30%-40%
25.0 2 5.7
28.3 2 3.7
27.9 + 4.7
31.0 r 8.5
32.5 + 8.8
< 30%
29.5 * 7.5
31 .o ?z 7.9
32.4 + 8.4
33.3 2 5.6
35.3 + 6.2
> 70%
1.3 + 0.5
1.3 k 0.4
1.3 + 0.4
2.3 + 0.7
2.9 k 1.2
< 40%
3.3 + 1.9
4.0 t 2.0
3.9 + 1.6
4.6 -c 1.9
2.9 2 2.0
30%-40%
3.3 k 1.6
4.0 * 2.0
4.2 + 1.7
3.8 2 1.7
4.3 -t 1.9
Function in Patients With Reduced Left Ventricular Undergoing Myocardial Revascularization
Function
Joachim Boldt, MD, Bernfried Zickmann, MD, Christoph Herold, Friedhelm Dapper, MD, and Gunter Hempelmann, Complex interrelationships exist between the right (RV) and the left ventricles (LV). Therefore, in 30 consecutive patients with reduced LV function (left ventricular ejection fraction [LVEF]) ~40% undergoing myocardial revascularization, RV hemodynamics were studied from the beginning of anesthesia until the end of the operation. The data were compared with 30 consecutive patients with normal LVEF (> 70%). Ventricular function was assessed during left heart catheterization, which was carried out within 1 month of the operation. In addition to standard hemodynamic variables, RV ejection fraction (RVEF), RV end-diastolic volume (RVEDV), and RV end-systolic volume (RVESV) were monitored by the thermodilution technique. The two groups did not differ preoperatively with regard to RVEF, pressure (MAP, PAP,
I
MPROVEMENTS in surgical technique, extracorporeal oxygenation, myocardial protection during cardiopulmonary bypass (CPB), and perioperative anesthetic management have led to improved results in patients with reduced the outcome in these myocardial function.’ 4 However, patients with markedly impaired left ventricular function [left ventricular ejection fraction (LVEF) < 40%] undergoing myocardial revascularization is still not as good as in patients with good myocardial performance.’ The left ventricle (LV) is perceived as the cardiac structure of greatest importance for pump function, and the role of the right ventricle (RV) has been questioned.‘.h However, inadequate overall cardiac performance secondary to RV dysfunction, caused by overload or ischemia, has become more and more apparent in recent studies.“’ Moreover, the RV and the LV are in series and mechanically coupled so that a disturbance in the mechanical function
of one ventricle
other.‘4-‘b of
the
Thus, right
undergoing
investigate alterations
there side
of
will influence
is growing the
heart,
interest
the behavior
of the
in the importance
particularly
in
patients
surgery.” This study was performed to whether reduced LV function is associated with in RV function. cardiac
MATERIALS
AND METHODS
Sixty patients undergoing elective myocardial revascularization were investigated after the study protocol was approved by the Institutional Ethics Board and informed consent was obtained. The patients were divided into 2 groups based on their LVEF obtained by left heart catheterization within 1 month of the operation: Group 1: 30 consecutive patients with a LVEF 70% (normal LV function). Exclusion criteria from the study were metabolic disorders, concomitant valvular diseases, unstable angina. pulmonary hypertension, and acute right heart failure. Premeditation with morphine, 0.15 mgikg, and flunitrazepam. 0.02 mgikg, was given I.5 hours before entering the operating room. Induction of anesthesia consisted of intravenous administration of fentanyl, 5 kg/kg. midazolam, 0.15 mg/kg, and pancuronium bromide, 0.1 mgikg. All patients were placed on mechanical ventilation with an F,O, of 1.0 and zero end-expiratory pressure. For maintenance of anesthesia, fentanyl (total dose: 35 Kg/kg). midazolam (total dose: 0.70 mgikg). and pancuronium bromide (total dose: 0.2X mgikg) were used. During and after CPB. midazolam (5 mg) and pancuronium hromide (2 mg) were given every 30 minutes. The total dosage of anesthetics was comparable for both groups. CPB was carried out using a membrane oxygenator (Sorin 41. Fa. Sorin, Torino. Italy) after 300 IU/kg of heparin were given to achieve anticoagulation. The extracorporeal circuit was primed with a mixture of 2,000 mL of crystalloids and 250 mL of 54 albumin. A monoatrial cannulation technique was used for drainage of the venous blood. The patients were kept nearly normothermic (lowest rectal temperature: 33.8 f 0.4”C) and a flow of 2.4 L/minim’ was maintained during the entire period of CPB. Ice cold Bretschneider’s cardioplegic solution was infused for myocardial protection. All patients were operated on by the same surgical team. During and after weaning from CPB, positive inotropic supper-t (calcium, epinephrine) was given when mean arterial pressure (MAP) was below 60 mm Hg or when cardiac index (CI) was les< than 2.0 L/minim’. Vasodilators (nitroglycerin) were administered when the pulmonary capillary wedge pressure (PCWP) was more than 20 mm Hg or systemic vascular resistance (SVR) was more than 1600 dyne s cm-‘. Volume (low molecular weight hydroxy ethyl starch solution) was infused to guarantee sufficient tilling (PCWP > 8 mm Hg). Volume administration and all pharmacological support were decided on hy an anesthesiologist not involved in the study. Hemodynamic monitoring consisted of measuring heart rate (HR), MAP, pulmonary artery pressure (PAP). right atrial pressure (RAP). and cardiac output (CO, thermodilution technique). Derived cardiovascular variables (SVR and CI) were calculated from standard formulae. The pulmonary artery catheter, inserted
Journalof Cardiothoraoc and VascularAnesthesra, Vol 6, No 1 (February), 1992: pp 24.28
RV FUNCTION
via the right jugular vein, was specifically designed to additionally measure right ventricular ejection fraction (RVEF), right ventricular end-systolic volume (RVESV), and right ventricular enddiastolic volume (RVEDV) using a thermodilution technique and a microprocessor (model REF-1; Edwards Laboratory, St Ana, CA). Normal values of RVEF assessed by this method ranged from 40% to 50%. Theoretical background material and the detailed technique have been described elsewhere.‘S-20 All measurements based on the thermodilution principle were performed at endexpiration in triplicate, and the mean values were used for statistical interpretation. Hemodynamic measurements were performed after induction of anesthesia in a hemodynamic steady state (baseline value), after sternotomy, before the start of CPB (pericardium open), immediately after weaning from CPB (pericardium open), and at the end of the operation (50 minutes after CPB). All results are expressed as mean (X) 2 standard deviation (SD). The data were analyzed using one-way and two-way analyses of variance with replication. Analysis of covariance was used to detect a relationship between two variables. P values < 0.05 were considered statistically significant.
IRVEF(%)] 3
,/I,, I,,,, ,,,,, ,,,,, ,,,,, /,,,_, ,,jl/ 1,,1,1 ,I,,, ,/,,,_
A
rr;;;g
T
C
I
I
P B
I
1 !
ii?EEE
ifSD
after
induction
50
1
atter
SternOtomY
after
Pericardiotomy
50
1RVEF(%)1
45
45
1
RESULTS
Demographic data and data from CPB are listed in Table 1. LVEF was 32.4 2 5.4% in group 1 and 77.4 2 4.7% in Group 1 was subdivided into group 1A group 2 (control). with moderately depressed LV function (LVEF, 30% to 40%) and group 1B with severely depressed LV function (LVEF, 70%
15.8 2 3.2
14.2 -t 3.0
14.5 2 2.6
16.8 2 2.4
16.8 2 3.1
< 40%
10.2 ?I 4.3
9.1 * 4.0
8.3 2 2.2
10.3 f 2.6
11.1 2 2.9
> 70%
7.6 2 2.0
7.9 + 2.1
7.5 2 2.0
8.9 + 2.0
9.8 + 1.9
70%
3.02 f 0.38
3.00 + 0.33
3.03 + 0.30
2.70 + 0.32
2.72 + 0.30
70%
1066 + 110
1064 + 129
1022 + 166
1100 f 200
1244 k 222
NOTE. x + SD.
might be responsible for the increased RV afterload. Thus, it is likely that the pulmonary circulation is affected by the same humoral factors that elevate systemic resistance. Finally, because of relatively poorer RV preservation during CPB,” postoperative RV function may be impaired by ischemic myocardial areas. Thus, because ischemia of the RV myocardium seems to be the limiting factor in the response to a pressure load, previously reduced RV function may produce serious deteriorations in RV performance during and after weaning from bypass. In this study, RVEF was monitored perioperatively because it is the method most frequently used to describe systolic function of the RV.16 It is influenced by contractility, afterload, HR, and, to some extent, by preload.9,13 When patients with normal LVEF and reduced LVEF ( 30%. Ventricular volumes (RVEDV, RVESV) were always elevated, whereas pressure monitoring (RAP, RVPsyst, RVEDP) did not allow correct evaluation of ventricular function, demonstrating that pressure variables often are not sensitive enough to assess reduced RV function. RV decompensation may not be associated with a low RV diastolic pressure because of the high compliance characteristics of this chamber.32 Other advantages of using the thermodilution technique are that moni-
toring of RVEF, RVEDV, and RVESV is unaffected by arbitrary and poorly reproducible zero-points for pressure transducers, and the technique can be used serially at the bedside or in the operating room. Knowledge of RV function in patients with reduced LV function seems to be crucial because the treatment of dysfunction of either the RV or the LV may differ widely.“’ More catecholamines and volume were necessary during and after termination of CPB in patients with severely reduced LVEF. The RV as well as the LV may have benefited from the positive inotropic support; none of the patients suffered from critical right heart failure. However, a distinction must be made between RV dysfunction and RV failure. In patients with additional increased impedance of the pulmonary circulation (interstitial edema, microembolism, massive release of vasoactive substances), right heart failure will occur earlier in patients with a severely reduced LVEF. It is concluded that a better understanding of the perioperative role of the RV in disease states that primarily affect the LV is necessary. LV abnormalities might influence RV function, depending on the degree of its effect on diastolic volume, systolic function, or RV afterload by passive elevation of PAP. This study demonstrated that a reduced LVEF does not limit RV function over a wide range. However, a LVEF of 70%
24.7 ? 3.6
24.1 2 4.5
26.2 + 6.3
28.3 + 6.6
30.0 + 5.2
< 40%
27.2 2 8.8
29.3 f 6.3
31.3 r 7.3
32.1 r 7.7
33.3 + 7.6
30%-40%
25.0 2 5.7
28.3 2 3.7
27.9 + 4.7
31.0 r 8.5
32.5 + 8.8
< 30%
29.5 * 7.5
31 .o ?z 7.9
32.4 + 8.4
33.3 2 5.6
35.3 + 6.2
> 70%
1.3 + 0.5
1.3 k 0.4
1.3 + 0.4
2.3 + 0.7
2.9 k 1.2
< 40%
3.3 + 1.9
4.0 t 2.0
3.9 + 1.6
4.6 -c 1.9
2.9 2 2.0
30%-40%
3.3 k 1.6
4.0 * 2.0
4.2 + 1.7
3.8 2 1.7
4.3 -t 1.9
