Echocardiographic Left Ventricular. Remodeling and Pseudohypertrophy as. Markers of Hypovolemia. An Experimental. Study on Bleeding and Volume ...
Echocardiographic Left Ventricular Remodeling and Pseudohypertrophy as Markers of Hypovolemia. An Experimental Study on Bleeding and Volume Repletion Elio Di Segni, MD, Sergei Preisman, Dan G. Ohad, DVM, Alexander Battier, MD, Valentina Boyko, Elieser Kaplinsky, MD, Azriel Perel, MD, and Zvi Vered, MD, Tel Aviv and Tel Hashomer, Israel
B a c k g r o u n d : M o n i t o r i n g intravascular v o l u m e d u r i n g surgery, especially in m a j o r cardiovascular procedures is necessary for a p p r o p r i a t e fluid r e s t o r a t i o n a n d t h e m a i n t e n a n c e o f an a d e q u a t e cardiac o u t p u t . In estimating preload, both standard hemodynamic a n d e c h o c a r d i o g r a p h i c p a r a m e t e r s have been limited. T h e p u r p o s e o f this s t u d y was to f u r t h e r define the effects o f i n d u c e d h y p o v o l e m i a o n the echocardiog r a p h i c p a r a m e t e r s . I n p a r t i c u l a r , we s o u g h t to s h o w w h e t h e r a decrease in e c h o c a r d i o g r a p h i c left ventricular area a n d v o l u m e was associated w i t h a significant increase in left v e n t r i c u l a r wall thickness (left vent r i c u l a r p s e u d o h y p e r t r o p h y ) a n d w i t h changes in L V f u n c t i o n . I n a d d i t i o n , we s o u g h t to investigate t h e effects o f r a p i d r e s t o r a t i o n o f b l o o d v o l u m e on cardiac d i m e n s i o n s a n d f u n c t i o n . M e t h o d s a n d results: Seven a n e s t h e t i z e d pigs u n d e r w e n t systemic a n d r i g h t h e a r t pressures a n d cardiac o u t p u t measurements. T w o - d i m e n s i o n a l e c h o c a r d i o g r a p h i c parasternal long- a n d short-axis views were o b t a i n e d d u r i n g g r a d e d b l e e d i n g by r a p i d w i t h d r a w a l o f b l o o d f r o m an arterial cannula, w i t h increments o f 5% each u p t o 30% o f calculated b l o o d volume. A f t e r complet i o n o f the b l e e d i n g , the entire a m o u n t o f the b l o o d w i t h d r a w n was r e t r a n s f u s e d w i t h i n 4 to 5 minutes. B o t h h e m o d y n a m i c a n d e c h o c a r d i o g r a p h i c measurem e n t s were p e r f o r m e d at baseline, i m m e d i a t e l y after t h e c o m p l e t i o n o f each stage o f b l e e d i n g a n d after b l o o d r e s t o r a t i o n . M e a n ( • s t a n d a r d d e v i a t i o n ) left v e n t r i c u l a r wall thickness (mean o f septal a n d poster i o r wall thickness) was 6.3 + 0.1 m m at baseline,
8.3 • 1.5 m m at peak bleeding, a n d 6.2 _+ 0.1 after r e s t o r a t i o n (p < 0.01). Left v e n t r i c u l a r mass d i d n o t change d u r i n g the experiment. Left v e n t r i c u l a r enddiastolic v o l u m e was 62.8 • 20.3 ml at baseline, 37.5 • 12.4 ml at peak b l e e d i n g (p < 0 . 0 0 0 1 ) , a n d 65.9 • 16.7 m l after b l o o d r e s t o r a t i o n (p < 0.001 c o m p a r e d w i t h 30% bleeding). H / r ratio ( p o s t e r i o r wall thickness d i v i d e d by left ventricular radius) increased f r o m 0.29 + 0.07 at baseline to 0.50 • 0.19 at peak b l e e d i n g r e t u r n i n g to 0.26 + 0 . 0 4 after r e s t o r a t i o n . Left v e n t r i c u l a r ejection fraction was 0.53 + 0.10 at baseline a n d 0.55 • 0.20 at peak b l e e d i n g ( n o t significant), decreasing to 0.38 • 0.11 after b l o o d r e s t o r a t i o n (p < 0.05 c o m p a r e d w i t h 30% b l e e d i n g ) . E n d - d i a s t o l i c v o l u m e c o r r e l a t e d closely w i t h r i g h t atrial pressure ( r = - 0 . 8 2 ) , capillary w e d g e pressure ( r = - 0 . 7 8 ) , a n d s t r o k e v o l u m e ( r = 0.74). Left v e n t r i c u l a r ejection fraction inversely corr e l a t e d w i t h left ventricular e n d - d i a s t o l i c v o l u m e ( r = - 0 . 4 8 ) a n d w i t h end-systolic wall stress ( r = - 0 . 6 2 ) . T h e changes in i n t e r v e n t r i c u l a r septal a n d p o s t e r i o r wall thickness were inversely related to left ventricular end-diastolic volume (r = -0.72 and - 0 . 3 5 , respectively). Conclusions: This s t u d y shows t h a t t r a n s i e n t concentric left v e n t r i c u l a r r e m o d e l i n g ( p s e u d o h y p e r t r o p h y ) , a p h e n o m e n o n previously described in cardiac t a m p o n a d e a n d d u r i n g r a p i d atrial p a c i n g is c o m m o n l y seen d u r i n g h y p o v o l e m i a . This new sign m a y f u r t h e r enhance the e c h o c a r d i o g r a p h i c e s t i m a t i o n o f left ventricular p r e l o a d . (J Am Soc Echocardiogr 1997;10:926-36.)
K J h a n g e s in b l o o d v o l u m e are f r e q u e n t d u r i n g surgery especially d u r i n g m a j o r cardiovascular p r o c e -
dures. B l o o d v o l u m e shifts cause changes in p r e l o a d , c o m m o n l y e s t i m a t e d by the m e a s u r e m e n t o f v e n t r i c ular filling pressures (right atrial a n d capillary w e d g e pressure). T h e limitations o f the h c m o d y n a m i c parameters in e s t i m a t i n g p r e l o a d are well l m o w n ~,2 a n d r e c e n t studies have stressed the limitations o f capillary w e d g e pressure, once c o n s i d e r e d an accurate reflect i o n o f the left ventricular (LV) p r e l o a d , in m c c h a n ically ventilated patients. 2 4 Echocardiography, especially transesophageal
From The Heart Institute, Department ofAnesthesiolog3, , Sheba Medical Center; The Neufeld Cardiac Research Institute, Tel Aviv University. Reprint requests: Elio Di Segni, MD, Heart Institute, Sheba Medical Center, Tel Hashomer 52621 Israel. Copyright 9 1997 by the American Society of Echocardiography. 0894-7317/97 $5.00 +0 2 7 / 1 / 8 2 8 1 5 926
Journal of the American Society, of Echocardiography Volume 10 Nmnber 9
Di Segni et al.
Table 1 Hemodynamic data in seven pigs
Table 1
(continued) Bleeding
Bleeding Pig Baseline
5%
10%
t-IR (beats/min) 149 118 llt 2 109 104 104 3 125 115 114 4 105 103 107 5 I06 111 112 6 95 98 102 7 132 115 114 Mean 117 109 109 SD 19 7.5 4.8 p < 0.05 l
15%
120 105 105 115 I15 117 138 116 11
20%
121 I21 113 i14 126 118 175 126 22
25%
127 136 139 137 123 121 193 139 25
30%
133 150 126 148 146 129 211 149 29
Re
110 128 149 147 142 120
173 138 21
17 6 4 4 8 8 3 7.1 4.8
15 6 4 4 8 7 4 6.9 3.9
15 6 3 3 7 6 3 6.1 4.3
14 5 4 3 7 6 2 5.9 3.9
17 14 9 11 11 15 7 12 3.5
CW-P (mm Hg) 1 13 18 2 12 11 3 10 9 4 10 10 5 13 12 6 12 ]0 7 10 10 Mean 12.3 11.4 SD, 3.2 3.0 p < 0.0001
20 8 8 8 10 10 9 10.4 4.3
21 7 7 6 10 8 7 9.4 5.3
16 8 6 6 8 9 6 8.4 3.5
16 8 6 6 9 8 4 8.1 3.8
20 16 13 i5 13 12 12 14.4 2.9
BP ( m m H g ) 104 2 120 3 I02 4 i15 5 115 6 114 7 122 Mean 113 SD 8 p < 0.01 1
104 I16 100 118 116 108 t14 110 7
106 122 106 118 115 104 110 111 7
Car~acou~ut(~min) 1 4.2 3.0 3.0 2 2.7 2.7 2.7 3 5.9 5.8 5.1 4 3.9 3.5 3.3 5 4.6 4.3 4.4 6 2.7 2.7 2.6 7 2.7 2.7 2.5 Mean 3.8 3.5 3,4 SD 1.2 1.2 1.0 p,
504 304
104 4
6
8
10 12 14 LVED a r e a crn2
1o4, o
16
1oo
200
300
ESWS g / c m 2
r=--0.48 90t 70~
so~ 3o4
I lo / 20
40 60 LVED v o l u m e rnl
80
1O0
Figure 5 Plots ofthc correlation between LV cjcction fraction (LVEF) and LV end-diastolic (LVED) area, LV end-diastolic volume, and end-systolic wall stress (ESWS). (e. g., compression, preload reduction, ventricular interdependence) may influence LV morphology, the only effect expected in bleeding is the reduction o f ventricular volume. As in previous studies, 9q~ as well as in this experiment, increase in LV thiclmess occurred without change o f LV mass, indicating that changes in wall thickness depended uniquely on volumetric changes. The present experiment, conducted under controlled conditions in which the LV wall thickness could have been accurately assessed in relation to LV volume, provided direct evidence that LV pseudohypertrophy is, indeed, the obligatory result o f reduced ventricular volume. Although the results o f this study should not be directly translated to the clinical practice, an example of possible clinical applications is shown in Figure 7. T h e LV geometric changes o f pseudohypertrophy are examples o f transient concentric LV remodeling, 14 resembling a similar but chronic alteration in LV geometry which has been described in a subset o f patients with hypertension, in whom reduced LV cavity and increased wall thiclmess with normal LV mass is associated with decreased cardiac output, increased peripheral vascular resistance and adverse prognosis. 14,2s,26 It has been suggested that the concentric LV remodeling occurring in hypertension results from contraction o f the intravascular volume. 2s Our experiment, showing that concentric LV remodeling is induced by hypovolemia, adds further
r=--0.63 18-1 16-1
9
,,
L)
g g
>,
12] 104 84 64 44 0.5
1i0
Sepfum
thickness
1,5
rnm
r=--0.72
100]
9 9 I
I
40
>,
2
0.5
1.0 Sepfum
thickness
1.5 mm
Figure 6 Plots of the correlation ofinterventricular seprum thickness and LV end-diastolic area (LVED) and volume.
934
Di S e g n i et al.
Figure 7 A, End-diastolic frame of the intraoperativc echocardiogram in the parasternal long-axis view obtained at the end of extracorporeal circulation for mitral valve repair in a 48-year-old patient. The left ventricular walls are severely thickened (both scptum and posterior wall 19 mm). B, Echocardiogram of the same patient, obtained on the same day, before surgery, shows normal left ventricular wall thicl~ness (septum 10 mm and posterior wall 9 mm). evidence to this hypothesis. A similar phenomenon was also observed after surgery for valvular regurgitation, 27 after hemodialysis, 2s and, recently, also in patients with implanted LV assist device studied by transesophageal echocardiography. 29 During all stages o f bleeding, LV ejection fraction did not change as diastolic and systolic volumes decreased in parallel. However, percent systolic thickcning, which is also considered an index o f LV function, s~ decreased, although not in a statistically significant measure. In a previous study on the effects o f rapid atrial pacing we also observed decreased percent systolic thickening associated with LV pseudohypertrophy and decreased LV volume. 1~ In the present study, decreased percent systolic thickening occurred without changes in 'heart rate. This suggests that percent systolic thickening is strongly
Journal of the American Society of Echocardiography November-December 1997
dependent on LV volume and LV wall thickness and cannot be taken as an indicator o f LV function when significant changes in these parameters also occur. In contrast to the stability o f LV ejection fraction during bleeding, LV ejection f?action markedly decreased after rapid restoration of blood volume. This decrease was associated with increase in end-systolic wall stress, a very reliable index o f afferload which is dependent on systolic blood pressure, LV diameter, and LV wall thickness. However, we cannot exclude that a decrease in coronary perfusion during hypotension may have contributed to the observed decrease in LV ejection fraction. Together with the transient deterioration in LV function during blood restoration we observed a marked LV enlargement in three o f the seven pigs. This observation may suggest that in a subset o f animals the increased afterload may cause overt LV deterioration leading to LV dilatation. Alternatively, it can be postulated that transient hypervolemia could have occurred in these animals from mobilization o f blood deposits in response to hemorrhage. It is c o m m o n clinical practice to replace blood loss and volume depletion gradually as rapid fluid restoration is thought to be detrimentalY The present experiment adds new data relevant to the understanding o f the sequence o f events during fluid replacement. During bleeding, catecholamines are produced in response to hypotension and the reduction of cardiac output, causing an increase in systemic vascular resistancel 3s During rapid fluid restoration the increase in systemic vascular resistance still persists, LV diameter suddenly increases, and LV wall thickness decreases. Rapid fluid replacement is associated with increase in afterload and may lead to impairment of LV function. Thus, fluid replacement should be carried out gradually to prevent the occurrence of LV failure. Limitations o f the Study Variations among pigs may have theoretically influe n c e d the results. In two o f seven pigs, h / r ratio changed less than in the rest o f the group (Table 2). Normalization o f the results was done using animal's weight and not body surface area, as with human beings. This was done because one can question the reliability o f using body surface area as a meaningful physiologic parameter for normalizing data in pigs in which the relationship between surface and weight is so different from that o f human beings. To avoid potential errors derived from inter-animal variability, we used the Fisher Z transformation o f Pearson correlation for the statistics o f the correlations between measured parameters.
Journal of the American Society of Echocardiography Volume 10 Number9
Limitation in echocardiographic measurements should be also pointed out. LV length may have been underestimated as we measured this value from the long-axis view and not from the apical view because in pigs apical views are often difficult to achieve. Special care was tal
