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Variations in ventricular weights of calf hearts at sea level
EXPERIMENTAL
AND
MOLECULAR
3, 320-324
PATHOLOGY
Variations
(1964)
in Ventricular
Weights
at Sea BERTRON Department
of Pathology,
M.
GROVES Baylor
Departments
of Pathology a:zd Department
S. DONALD
University
and Pediatrics, of Pathology,
Calf
Hearts
Level1
AND
HARVEY
of
GREENBERG
College
of
Medicine,
Houston,
Texas
S. ROSENBERG Baylor Texas
University Children’s
College Hospital,
of Medicine, Houston, Houston, Texas
Texas
AND
J. D. Department
of Physiology
and
the
MCCRADY
Vivarium, Houston,
Received
Baylor Texas
August
University
College
of Medicine,
25, 1963
INTRODUCTION The newborn calf has been shown to be a good subject for the production of experimental hypertension (McCrady et al., 1963 ; Vogel et al., 1964). Cardiovascular physiology of normal cattle and those with pulmonary hypertension have been amply studied (Hecht et al., 1962a, b; Lewis, 1913; Reeves et al., 1962; Will et al., 1962). Morphologic observations have received less attention. The ratio of the weights of the right and left ventricular myocardium have been measured at high altitudes and in the presence of pulmonary hypertension (Alexander et al., 1960; Hecht et al., 1959; Vogel et al., 1964). No information has been available concerning the normal maturation of the right and left ventricles of the calf kept at sea level. Right ventricular hypertrophy is an important parameter in the study of pulmonary hypertension. There is no unanimity in the method of quantitating the degree of hypertrophy. In 1913, Lewis trisected the human ventricular myocardium into the septum, the free right ventricular wall, and the free left ventricular wall. The weight of each was expressed as a ratio to the total ventricular weight. Fulton et aZ. (1952) used the same method and concluded that the most significant expression of right ventricular hypertrophy in man was the ratio of the weight of the free right ventricular wall to the weight of the heart. Alexander et al. (1960) and Hecht et al. (1959) used similar methods for the study of bovine hearts. In the method described by Herrmann and Wilson in 1921, the heart was cut in slices perpendicular to the long axis, and the right and left ventricles were divided by cutting along a “natural line of division” within the interventricular septum. Spalteholz (1923) illustrated this anatomic division of the right and left ventricles (Fig. 1). Emery and MacDonald (1960) and Arias-Stella and Recavarren (1962) utilized this method in studies of the human heart. With the method of Lewis, the portion of the right ventricular wall within the 1 Supported
in part
by NlH
research
grant
H-6964 320
and USPA
HP15435,
Project
6.
CALF
321
HEARTS
LE :FT VENT ‘RICL
FIG.
1.
Sketch
of human
ICLE
heart
illustrating
the division
of muscle
fibers
between
right
and
left
ventricles.
septum cannot be properly evaluated since this is weighed as a portion of the septum. The method of Herrmann and Wilson was chosen as the most representative means for determining the individual ventricular weight. METHOD Hearts were obtained from 21 male calves that ranged in age from 1 day to 12 months, Three hearts were from calves less than 5 days old, 12 hearts were from calves 6 months of age, and 6 hearts were from calves 12 months old. All of these animals had lived at sea level. The great vessels and a portion of both atria were removed from the fresh hearts. The ventricular chambers were washed free of blood clots and packed with cotton to approximate the normal size and shape. The specimens were then fixed in 20% formalin for 1 week (due to the thickness of the bovine myocardium, the standard lOc/r formalin proved to be unsatisfactory for proper fixation). After fixation, the atrio-ventricular and semilunar valves, coronary vessels, and epicardial fat were removed with the remaining atria1 tissue. The intact ventricles were measured on the posterior surface from base to apex and were divided into five slices of equal thickness by cutting the heart perpendicular to the long axis. To complete fixation, the segments were placed in formalin for another 2-4 days. To separate the right and left ventricular components of each slice, the interventricular septum was divided with a sharp scalpel along the line of demarcation formed by the scroll muscle layers passing through the center of the septum in an anteriorposterior direction (Herrmann and Wilson, 1921) (Fig. 2). The right and left ventricular portions of each level were weighed. The right ventricular weight (RVW) and left ventricular weight (LVW) were obtained by totaling the weights of the individual segments. The total ventricular weight (TVW) was the sum of the RVW and LVR.
322
BERTRON
FIG. 2. A transverse septal fibers.
cut section
M.
GROVES
of the ventricles.
Note
ET
AL.
the directional
flow
of the interventricular
0.4 0.3 0.2 0. I 0.0
FIG.
within
3. Correlation the horizontal
of ventricular vars.
0
weight
3 ratios
MON6f”S with
9 age of calves.
12 Standard
deviation
is shown
CALF
323
HEARTS
RESULTS The data from our specimens were obtained by using the method of Herrmann and Wilson (1921) as modified by Arias-Stella and Recavarren (1962). The RVW/ LVW ratio varied significantly with the age of the calves (Fig. 3). During the first 5 days of life, there is a relative predominance of the right ventricular weight with a mean RVW/LVW of 1.00 (SD = 0.136; SE = 0.078). By 6 months the weight of the left ventricle has increased in proportion greater than that of the right and the mean RVW/LVW ratio is 0.58 (SD = 0.042; SE = 0.012). This ratio remained constant with further aging, for the mean RVW/LVW at 12 months is 0.59 (SD = 0.021; SE = 0.003). The mean ventricular weight ratios are tabulated in Table I. TABLE VENTRICULAR
No. calves 3
Age (months) 1-j
days
12
6
6
12
I
WEIGHT
RVW/LVW Mean SD SE Mean SD SE Mean SD SE
1.00
0.14 0.08 0.58 0.04 0.01
0.59 0.02 0.003
RATIOS
LVW/RVW Mean SD SE Mean SD SE Mean SD SE
1.02 0.13 0.09 1.68 0.02 0.05 1.70 0.07 0.03
RVW/TVW Mean SD SE Mean SD SE Mean SD SE
0.50 0.13 0.09 0.37 0.02 0.01 0.38 0.01 0.004
DISCUSSION As with the human (Emery and MacDonald, 1960; Emery and Mithal, 1961), there is a relative right ventricular preponderance in the calf at birth. In the fetus and the newborn the right and left ventricular weights are equal. In the interval from 2 to 6 months, the left ventricle grows more rapidly than the right (Keen, 1955). In the human infant at 6 months, the RVW/LV?V has been recorded as 0.54 (Arias-Stella and Recavarren, 1962). This is obviously the same order of magnitude determined for the calf at 6 months, i.e., 0.58. The relative preponderance of the right ventricle in the newborn parallels the increased pulmonary peripheral resistance during this period. In the intrauterine state the airless lung is largely bypassed because of the right to left shunt through the foramen ovale and the ductus arteriosus. The right to left shunt is maintained by the small arteries with their thick walls and small lumens. This vascular structure in the fetus and neonate maintains the high resistance to blood flow. With the onset of respiration at birth there is a drop in pulmonary vascular resistance to blood flow. The morphology of the pulmonary vessels and the relative weight of the right ventricular myocardium gradually change to the mature status (Rosenberg et al., 1960). The structural changes are slower than the physiological changes. The pulmonary vascular changes reach a mature configuration at about 2 months. The adult ratio of right to left ventricle is reached by 6 months. If pulmonary hypertension is maintained, as by a congenital cardiac malformation, there is persistence of the immature pulmonary arterial configuration and of the right ventricular preponderance. There is a temptation to use the term LLhypertrophy” with respect to the pulmonary vessels and the right ventricular myocardium. This may not
324
BERTRON
M.
GROVES
ET AL.
be valid since the size of these structures is relevant only in relation to the age and physiologic state. The data derived in the present study will serve as a reference for the designation of right ventricular hypertrophy in experimental pulmonary hypertension in the calf. SUMMARY In order to provide data on the variations in ventricular weights of calf hearts at sea level, the ratio of right ventricular weight (RVW) to left ventricular weight (LVW) was determined for 21 hearts of normal calves ranging in age from 1 day to 12 months, Hearts of calves less than 5 days of age had a mean RVW/LVW of 1.00 (SD = 0.136; SE = 0.078). Twelve 6-month-old calves had RVW/LVW of 0.58 (SD z 0.042; SE = 0.012). Six 12-month-old specimens had a mean RVW/LVW of 0.59 (SD = 0.012 ; SE = 0.003). At birth the RVW predominates, At the age of 6 months the adult RVW/LVW ratio has been established. These data are quite similar to those previously established for the human. REFERENCES ALEXANDER, A. F., WILL, D. H., GROVER, R. F., and REEVES, J. T. (1960). Pulmonary hypertension and right ventricular hypertrophy in cattle at high altitude, Am. J. Vet. Res. 21, 199-204. ARIAS-STELLA, J., and RECAVARREN, S. (1962). Right ventricular hypertrophy in native children living at high altitude. Am. J. Pathol. 61, 55-64. EMERY, J. L., and MACDONALD, M. S. (1960). The weight of the ventricles in the later weeks of intra-uterine life. Brit. Heart J. 22, 563-570. EMERY, J. L., and MITHAL, A. (1961). Weight of cardiac ventricles at and after birth. Brit. Heart J. 23, 313-316. FULTON, R. M., HUTCHINSON, E. C., and JONES, M. Ventricular weight in cardiac hyper(1952). trophy. Brit. Heart J. 14, 413-420. HECHT, H. H., LANGE, R. L., CARNES, W. H., KUIDA, H., and BLAKE, J. T. (1959). Brisket disease I: General aspects of pulmonary hypertensive disease in cattle. Trans. Assoc. Am. Physicians x2,157-172. HECHT, H.
H., KUIDA, H., LANGE, R. L., THORNE, J. L., and BROWN, A. M. (1962a). Brisket disease II: Clinical features and hemodynamic observations in altitude-dependent right heart failure of cattle. Am. J. Med. 32, 171-183. HECHT, H. H., KUIDA, H., and TSAGARIS, T. J. (1962b). Brisket disease IV: Impairment of left ventricular function in a form of car pulmonale. Trans. Assoc. Am. Physicians 75, 263-276. HERRMANN, G. R., and WILSON, F. N. (1921). Ventricular hypertrophy: A comparison of electrocardiographic and post-mortem observations. Heart 9, 92-147. KEEN, E. N. (1955). The postnatal development of the human cardiac ventricles. J. Anat. 89, 484-502. KUIDA, H., BROWN, A. M., LANGE, R. L., and HECHT, H. H. (1961). Cardiovascular studies on normal calves. Am. J. Physiol. 200, 247. LEWIS, T. (1913). Observations upon ventricular hypertrophy, with especial reference to preponderance of one or other chamber. Heart 5, 367-403. MCCRADY, J. D., GREENBERG, S. D., HALLMAN, G. L., MCNAMARA, D. G., ROSENBERG, H. S., O’NEAL, R. M., and KEATS, A. S. (1963). The use of the newborn calf in cardiovascular research. Cardiovascular Res. Center Bull. 1, 110-115. REEVES, J. T., GROVER, R. F., WILL, D. H. and ALEXANDER, M. D. (1962). Hemodynamics in normal cattle. Circulation Res. 10, 166-171. ROSENBERG, H. S., MCNAMARA, D. G., LEACHMAN, R., and BUZZI, R. (1960). Pulmonary vascular structure of children with interventricular septal defect. Arch. Pathol. 70, 141-148. <‘Hand-Atlas of Human Anatomy” SPALTEHOLZ, W. (1923). Vol. II, pp. 388-390. Lippincott, Philadelphia, Pennsylvania. S. G. (1963). An Experimental VOGEL, J. H. K., A~ERILL, K. H., POOL, P. E., and BLOUNT, pulmonary hypertension in the newborn calf. Circulation Res. 13, X7-571. WILL, D. H., ALEXANDER, A. F., REEVES, J. T., and GROVER, R. F. (1962). High altitude-induced pulmonary hypertension in normal cattle. Circzllation Res. 10, 172-177.
AND
MOLECULAR
3, 320-324
PATHOLOGY
Variations
(1964)
in Ventricular
Weights
at Sea BERTRON Department
of Pathology,
M.
GROVES Baylor
Departments
of Pathology a:zd Department
S. DONALD
University
and Pediatrics, of Pathology,
Calf
Hearts
Level1
AND
HARVEY
of
GREENBERG
College
of
Medicine,
Houston,
Texas
S. ROSENBERG Baylor Texas
University Children’s
College Hospital,
of Medicine, Houston, Houston, Texas
Texas
AND
J. D. Department
of Physiology
and
the
MCCRADY
Vivarium, Houston,
Received
Baylor Texas
August
University
College
of Medicine,
25, 1963
INTRODUCTION The newborn calf has been shown to be a good subject for the production of experimental hypertension (McCrady et al., 1963 ; Vogel et al., 1964). Cardiovascular physiology of normal cattle and those with pulmonary hypertension have been amply studied (Hecht et al., 1962a, b; Lewis, 1913; Reeves et al., 1962; Will et al., 1962). Morphologic observations have received less attention. The ratio of the weights of the right and left ventricular myocardium have been measured at high altitudes and in the presence of pulmonary hypertension (Alexander et al., 1960; Hecht et al., 1959; Vogel et al., 1964). No information has been available concerning the normal maturation of the right and left ventricles of the calf kept at sea level. Right ventricular hypertrophy is an important parameter in the study of pulmonary hypertension. There is no unanimity in the method of quantitating the degree of hypertrophy. In 1913, Lewis trisected the human ventricular myocardium into the septum, the free right ventricular wall, and the free left ventricular wall. The weight of each was expressed as a ratio to the total ventricular weight. Fulton et aZ. (1952) used the same method and concluded that the most significant expression of right ventricular hypertrophy in man was the ratio of the weight of the free right ventricular wall to the weight of the heart. Alexander et al. (1960) and Hecht et al. (1959) used similar methods for the study of bovine hearts. In the method described by Herrmann and Wilson in 1921, the heart was cut in slices perpendicular to the long axis, and the right and left ventricles were divided by cutting along a “natural line of division” within the interventricular septum. Spalteholz (1923) illustrated this anatomic division of the right and left ventricles (Fig. 1). Emery and MacDonald (1960) and Arias-Stella and Recavarren (1962) utilized this method in studies of the human heart. With the method of Lewis, the portion of the right ventricular wall within the 1 Supported
in part
by NlH
research
grant
H-6964 320
and USPA
HP15435,
Project
6.
CALF
321
HEARTS
LE :FT VENT ‘RICL
FIG.
1.
Sketch
of human
ICLE
heart
illustrating
the division
of muscle
fibers
between
right
and
left
ventricles.
septum cannot be properly evaluated since this is weighed as a portion of the septum. The method of Herrmann and Wilson was chosen as the most representative means for determining the individual ventricular weight. METHOD Hearts were obtained from 21 male calves that ranged in age from 1 day to 12 months, Three hearts were from calves less than 5 days old, 12 hearts were from calves 6 months of age, and 6 hearts were from calves 12 months old. All of these animals had lived at sea level. The great vessels and a portion of both atria were removed from the fresh hearts. The ventricular chambers were washed free of blood clots and packed with cotton to approximate the normal size and shape. The specimens were then fixed in 20% formalin for 1 week (due to the thickness of the bovine myocardium, the standard lOc/r formalin proved to be unsatisfactory for proper fixation). After fixation, the atrio-ventricular and semilunar valves, coronary vessels, and epicardial fat were removed with the remaining atria1 tissue. The intact ventricles were measured on the posterior surface from base to apex and were divided into five slices of equal thickness by cutting the heart perpendicular to the long axis. To complete fixation, the segments were placed in formalin for another 2-4 days. To separate the right and left ventricular components of each slice, the interventricular septum was divided with a sharp scalpel along the line of demarcation formed by the scroll muscle layers passing through the center of the septum in an anteriorposterior direction (Herrmann and Wilson, 1921) (Fig. 2). The right and left ventricular portions of each level were weighed. The right ventricular weight (RVW) and left ventricular weight (LVW) were obtained by totaling the weights of the individual segments. The total ventricular weight (TVW) was the sum of the RVW and LVR.
322
BERTRON
FIG. 2. A transverse septal fibers.
cut section
M.
GROVES
of the ventricles.
Note
ET
AL.
the directional
flow
of the interventricular
0.4 0.3 0.2 0. I 0.0
FIG.
within
3. Correlation the horizontal
of ventricular vars.
0
weight
3 ratios
MON6f”S with
9 age of calves.
12 Standard
deviation
is shown
CALF
323
HEARTS
RESULTS The data from our specimens were obtained by using the method of Herrmann and Wilson (1921) as modified by Arias-Stella and Recavarren (1962). The RVW/ LVW ratio varied significantly with the age of the calves (Fig. 3). During the first 5 days of life, there is a relative predominance of the right ventricular weight with a mean RVW/LVW of 1.00 (SD = 0.136; SE = 0.078). By 6 months the weight of the left ventricle has increased in proportion greater than that of the right and the mean RVW/LVW ratio is 0.58 (SD = 0.042; SE = 0.012). This ratio remained constant with further aging, for the mean RVW/LVW at 12 months is 0.59 (SD = 0.021; SE = 0.003). The mean ventricular weight ratios are tabulated in Table I. TABLE VENTRICULAR
No. calves 3
Age (months) 1-j
days
12
6
6
12
I
WEIGHT
RVW/LVW Mean SD SE Mean SD SE Mean SD SE
1.00
0.14 0.08 0.58 0.04 0.01
0.59 0.02 0.003
RATIOS
LVW/RVW Mean SD SE Mean SD SE Mean SD SE
1.02 0.13 0.09 1.68 0.02 0.05 1.70 0.07 0.03
RVW/TVW Mean SD SE Mean SD SE Mean SD SE
0.50 0.13 0.09 0.37 0.02 0.01 0.38 0.01 0.004
DISCUSSION As with the human (Emery and MacDonald, 1960; Emery and Mithal, 1961), there is a relative right ventricular preponderance in the calf at birth. In the fetus and the newborn the right and left ventricular weights are equal. In the interval from 2 to 6 months, the left ventricle grows more rapidly than the right (Keen, 1955). In the human infant at 6 months, the RVW/LV?V has been recorded as 0.54 (Arias-Stella and Recavarren, 1962). This is obviously the same order of magnitude determined for the calf at 6 months, i.e., 0.58. The relative preponderance of the right ventricle in the newborn parallels the increased pulmonary peripheral resistance during this period. In the intrauterine state the airless lung is largely bypassed because of the right to left shunt through the foramen ovale and the ductus arteriosus. The right to left shunt is maintained by the small arteries with their thick walls and small lumens. This vascular structure in the fetus and neonate maintains the high resistance to blood flow. With the onset of respiration at birth there is a drop in pulmonary vascular resistance to blood flow. The morphology of the pulmonary vessels and the relative weight of the right ventricular myocardium gradually change to the mature status (Rosenberg et al., 1960). The structural changes are slower than the physiological changes. The pulmonary vascular changes reach a mature configuration at about 2 months. The adult ratio of right to left ventricle is reached by 6 months. If pulmonary hypertension is maintained, as by a congenital cardiac malformation, there is persistence of the immature pulmonary arterial configuration and of the right ventricular preponderance. There is a temptation to use the term LLhypertrophy” with respect to the pulmonary vessels and the right ventricular myocardium. This may not
324
BERTRON
M.
GROVES
ET AL.
be valid since the size of these structures is relevant only in relation to the age and physiologic state. The data derived in the present study will serve as a reference for the designation of right ventricular hypertrophy in experimental pulmonary hypertension in the calf. SUMMARY In order to provide data on the variations in ventricular weights of calf hearts at sea level, the ratio of right ventricular weight (RVW) to left ventricular weight (LVW) was determined for 21 hearts of normal calves ranging in age from 1 day to 12 months, Hearts of calves less than 5 days of age had a mean RVW/LVW of 1.00 (SD = 0.136; SE = 0.078). Twelve 6-month-old calves had RVW/LVW of 0.58 (SD z 0.042; SE = 0.012). Six 12-month-old specimens had a mean RVW/LVW of 0.59 (SD = 0.012 ; SE = 0.003). At birth the RVW predominates, At the age of 6 months the adult RVW/LVW ratio has been established. These data are quite similar to those previously established for the human. REFERENCES ALEXANDER, A. F., WILL, D. H., GROVER, R. F., and REEVES, J. T. (1960). Pulmonary hypertension and right ventricular hypertrophy in cattle at high altitude, Am. J. Vet. Res. 21, 199-204. ARIAS-STELLA, J., and RECAVARREN, S. (1962). Right ventricular hypertrophy in native children living at high altitude. Am. J. Pathol. 61, 55-64. EMERY, J. L., and MACDONALD, M. S. (1960). The weight of the ventricles in the later weeks of intra-uterine life. Brit. Heart J. 22, 563-570. EMERY, J. L., and MITHAL, A. (1961). Weight of cardiac ventricles at and after birth. Brit. Heart J. 23, 313-316. FULTON, R. M., HUTCHINSON, E. C., and JONES, M. Ventricular weight in cardiac hyper(1952). trophy. Brit. Heart J. 14, 413-420. HECHT, H. H., LANGE, R. L., CARNES, W. H., KUIDA, H., and BLAKE, J. T. (1959). Brisket disease I: General aspects of pulmonary hypertensive disease in cattle. Trans. Assoc. Am. Physicians x2,157-172. HECHT, H.
H., KUIDA, H., LANGE, R. L., THORNE, J. L., and BROWN, A. M. (1962a). Brisket disease II: Clinical features and hemodynamic observations in altitude-dependent right heart failure of cattle. Am. J. Med. 32, 171-183. HECHT, H. H., KUIDA, H., and TSAGARIS, T. J. (1962b). Brisket disease IV: Impairment of left ventricular function in a form of car pulmonale. Trans. Assoc. Am. Physicians 75, 263-276. HERRMANN, G. R., and WILSON, F. N. (1921). Ventricular hypertrophy: A comparison of electrocardiographic and post-mortem observations. Heart 9, 92-147. KEEN, E. N. (1955). The postnatal development of the human cardiac ventricles. J. Anat. 89, 484-502. KUIDA, H., BROWN, A. M., LANGE, R. L., and HECHT, H. H. (1961). Cardiovascular studies on normal calves. Am. J. Physiol. 200, 247. LEWIS, T. (1913). Observations upon ventricular hypertrophy, with especial reference to preponderance of one or other chamber. Heart 5, 367-403. MCCRADY, J. D., GREENBERG, S. D., HALLMAN, G. L., MCNAMARA, D. G., ROSENBERG, H. S., O’NEAL, R. M., and KEATS, A. S. (1963). The use of the newborn calf in cardiovascular research. Cardiovascular Res. Center Bull. 1, 110-115. REEVES, J. T., GROVER, R. F., WILL, D. H. and ALEXANDER, M. D. (1962). Hemodynamics in normal cattle. Circulation Res. 10, 166-171. ROSENBERG, H. S., MCNAMARA, D. G., LEACHMAN, R., and BUZZI, R. (1960). Pulmonary vascular structure of children with interventricular septal defect. Arch. Pathol. 70, 141-148. <‘Hand-Atlas of Human Anatomy” SPALTEHOLZ, W. (1923). Vol. II, pp. 388-390. Lippincott, Philadelphia, Pennsylvania. S. G. (1963). An Experimental VOGEL, J. H. K., A~ERILL, K. H., POOL, P. E., and BLOUNT, pulmonary hypertension in the newborn calf. Circulation Res. 13, X7-571. WILL, D. H., ALEXANDER, A. F., REEVES, J. T., and GROVER, R. F. (1962). High altitude-induced pulmonary hypertension in normal cattle. Circzllation Res. 10, 172-177.