- Email: [email protected]
Relation of left ventricular function and Na,K-pump concentration in suspected idiopathic dilated cardiomyopathy
CARDIOMYOPATHY
Relationof left VentricularFunctionand Na,K-Pump Concentrationin SuspectedIdiopathicDilated Cardiomyopathy AAGE NmGAARD, ULRIK BAANDRUP,
MD, JENS P. BAGGER, MD, PREBEN BJERREGAARD, MD, MD, KELD KJELDSEN, MD, and POUL E.B. THOMSEN, MD
highly significant (n = 24, r = 0.61, p
The possible relation between Na,K-pump concentration and left ventricular (LV) function was studied in 24 patients with suspected idiopathic dilated cardiomyopathy. This was done by measurement of SH-ouabain binding to biopsies obtained during ieftsided heart catheterization. in ail patients light microscopy of biopsies was compatible with dilated cardiomyopathy. Nineteen patients had impaired LV function as defined by NYHAIWHO and a Na,Kpump concentration of 331 f 19 pmoi/g wet weight, wheras 5 patients had normal LV function and a Na,K-pump concentration of 559 f 62 pmoi/ g wet weight (p
(Am J Cardioi 1968;61:1312-1315)
T
he Na,K-ATPase or Na,K-pump is of major importance in myocardial function. Thus, the active transport of Na and K across the cell membrane by the Na,K-pump is essential for excitability and contractility.l The reuptake by the Na,K-pump of K lost from the cell during the action potential prevents a possible arrhythmogenic rise of interstitial K.2 By maintaining the Na gradient across the cell membrane and associated Na-Ca exchange, the Na,K-pump plays a significant role in cellular Ca clearancee3 Finally, the Na,Kpump is accepted to be the cellular receptor for digitalFrom the Departments of Cardiology and Pathology, Aarhus Municipal Hospital, and Institute of Physiology, University of Aarhus, Denmark. This study was supported in part by the Danish Heart Foundation and the Danish Medical Research Council. Manuscript received October 1, 1987; revised manuscript received and accepted February 23,1988. Address for reprints: Aage Nergaard, MD, Department of Cardiology, Skejby Hospital, DK-8200 Aarhus N, Denmark.
1312
is glycosides.4 A decrease in Na,K-ATPase activity in the cardiac plasma membrane has been shown to be one of the earliest abnormalities during the course of hereditary cardiomyopathy in the hamster5r6 and it might be of importance in the associated intracellular Ca accumulation, mitochondrial calcification and cell necrosis.7 To our knowledge, the Na,K-pump has never been assessed in human cardiomyopathy. In this study, we investigated the concentration of Na,Kpumps in the left myocardium from patients suspected of dilated cardiomyopathy.
Methods Patients: The study was approved by the local ethics committee according to the Helsinki Declaration II. During a 2-year period (1985 to 19861,24 patients (12 men and 12 women, ages 25 to 62 years, mean 44) with suspected idiopathic dilated cardiomyopathy underwent a diagnostic left-sided heart catheterization. At the time of examination, 2 patients were treated with
June 1, 1988
digoxin, 14 with both digoxin and diuretics, and 8 with diuretics. All patients were normotensive. Serum potassium was in the normal range (3.5 to 5.0 mmol/liter). Heart catheterization: The left side of the heart was catheterized by way of the femoral artery. The left ventricular (LV) end-diastolic pressure was recorded. Biplane (18 patients] or single-plane (6) LV angiography and coronary arteriography were performed. Four endomycardial biopsies of 1 to 2 mg were taken from the apical portion of the LV wall using a Cordis biopsy forceps. Three of the biopsies were processed for light microscopy while the remaining 1 biopsy was frozen at -20°C until the determination of 3H-ouabain binding site concentration. 3H-ouabain binding: This assay was performed as previously described.8 Biopsy specimens were prewashed for 2 X 10 minutes at 0°C in a TRIS sucrose buffer (pH 7.3) containing 1 mmol/liter vanadate (NaVO& 3 mmol/liter MgS04, 10 mmol/liter TRIS chloride and 250 mmol/liter sucrose. Incubation took place in the TRIS sucrose buffer containing 1 X low6 mol/liter 3H-ouabain at 37'C for 2 X 60 minutes. This was followed by a wash at 0°C in unlabelled buffer for another 4 X 30 minutes to remove 3H-ouabain from the extracellular space. After blotting, the samples were weighed and 5% trichloroacetic acid was added. After extraction overnight and liquid scintillation counting, the amount of 3H-ouabain bound to the biopsies was calculated based on the specific activity of the incubation medium. After correcting for unspecific uptake in the presence of surplus of unlabelled ouabain, it was expressed as pmol/g wet weight of muscle tissue. Statistics: Ventricular volumes were determined from the angiography by the width-length method9 and expressed as ml/m2 of body surface area. The ejection fraction was defined as the ratio of angiographic stroke volume to end-diastolic volume. After elastic Van Gieson staining, the volume fraction of collagen tissue in the biopsies was assessed by point counting.lO Results are given as mean value f standard error of the mean. Statistical significance of any difference was determined using the &tailed t test for nonpaired groups of observations. Linear regression analysis was performed using the method of least squares. A p <0.05 was considered statistically significant.
Results Left-sided heart catheterization exposed neither congenital heart diseases, valvular diseases nor abnormalities in the coronary arteries. Nineteen patients had impaired LV function defined as LV end-diastolic volume 1100 ml/m2 and ejection fraction SO.45compatible with dilated cardiomyopathy.ll A history of heavy drinking was confirmed in 4 patients and 3 patients had a history suggesting previous myocarditis. Five patients had angiographically-determined normal LV function. No patient in this group had a history of drinking, whereas 3 patients had a history suggesting previous myocarditis. Light microscopy of LV biopsies from all 24 patients showed varying degrees of
THE AMERICAN
JOURNAL
OF CARDIOLOGY
1313
Volume 61
TABLE I Clinical Characteristics, Hemodynamic Parameters, Light Microscopy Findings and Na,K-Pump Concentration Normal LV Function (n = 5) 40 f II 8fl 61 f5 63 f 7.6 f 559 f
Age (~0 NYHA class LVEDP (mm Hg) LVEDV (ml/ms) EF (%) VFC (%) Na,K-pumps (pmollg wet weight)
4
5 3.9 62
Impaired LV Function (n = 19) 45 f 2 III-IV 23 f 2 140 f 14 31 f 2 5.1 f 0.6 331 f 19
p Value NS
EF = ejection fraction; NYHA class = New York Heart Association functional class; LV = left ventricle; LVEDP = left ventricular end-diastolic pressure; LVEDV = left ventricular end-diastolic volume; NS = not significant (p 20.05): VFC = volume fraction of collagen.
TABLE II Correlation Matrix of Hemodynamic Parameters, Microscopy Findings and Na,K-Pump Concentration
Age LVEDP LVEDV EF VFC Na,K-pumps
Age
LVEDP
LVEDV
EF
1.00 0.05 -0.18 -0.10 -0.40 -0.20
1.00 0.47’ -0.61’ -0.10 -0.37
1.00 -0.59’ 0.13 -0.49’
1.00 0.06 0.81’
VFC
1 .oo -0.08
Light
Na,K-Pumps
1 .oo
* p <0.05. EF = ejection fraction; LVEDP = left ventricular end-diastolic pressure; LVEDV = left ventricular end-diastolic volume: VFC = volume fraction of collagen.
nuclear hypertrophy, fiber attenuation, smooth-muscle cell hypertrophy or fibrosis compatible with dilated cardiomyopathy.1° The degree of fibrosis was evaluated by measurement of volume fraction of collagen tissue in the biopsies, The Na,K-pump concentration was determined in the LV biopsies by measuring 3Houabain binding. The clinical characteristics, hemodynamic parameters, light microscopy findings and Na,K-pump concentration in patients with normal and impaired LV function, respectively, are listed in Table I. Table II lists the correlation coefficients between the hemodynamic parameters, light microscopy findings and Na,K-pump concentration in all 24 patients. The correlations between diastolic LV function estimated by LV end-diastolic pressure or estimated by LV end-diastolic volume and Na,K-pump concentration were not significant and only weakly significant, respectively. As can be seen in Figure 1, there was a highly significant correlation between Na,K-pump concentration and systolic function of LV, as estimated by ejection fraction in all 24 patients. Separate correlation analysis between Na,K-pump concentration and ejection fraction in the 16 patients receiving digoxin and in the 8 patients taking diuretics alone also showed significance (r = 0.69, p <0.005 and r = 0.89, p <0.005, respectively). There were no correlations between the
1314
HEART Na,K-PUMPS
AND DILATED
CARDIOMYOPATHY
volume fraction of collagen tissue and the hemodynamic parameters or the Na,K-pump concentration in all 24 patients (Table II).
Discussion The Na,K-pump in the human myocardium has only been assessedin very few studies8,12and, to our knowledge, never in cardiomyopathic patients. The present study demonstrates a decrease in 3H-ouabain binding site concentration with dilated cardiomyopathy. This might be assumed to represent a decrease in Na,K-pump concentration because 3H-ouabain binding to endomyocardial biopsies has proved adequate for assessment of Na,K-pumps in the human myocardium.8 During digoxin treatment a tissue concentration of approximately 75 pmollg wet weight has been found in the myocardium. l3 This might interfere with 3Houabain binding at receptor level. However, separate correlation analyses between Na,K-pump concentration and ejection fraction in patients receiving digoxin or diuretics alone showed significance, which indicates that the decrease in Na,K-pump concentration with impaired LV function is not the simple outcome of digoxin treatment. In hamster hereditary cardiomyopathy, the progression of cardiac damage is associated with intracellular Ca accumulation followed by cell necrosis, congestive heart failure and ultimately death.7 In human dilated cardiomyopathy, calcification is not a characteristic finding,‘0 whereas changes in several myocardial enzymes have been demonstrated. Thus, endomyocardial biopsies of the LV in patients with dilated cardiomyopathy showed a decrease in myofibrillar Ca-ATPase and activity of several mitochondrial en1.0 r =
0.81
p < 0.001 n = 24
1
0.8
0 i
g 3
O.%-
References
s tt: fz 3
$ .C) w
zymes.14In hypertrophic cardiomyopathy these enzymatic activities were normal. Furthermore, a correlation between the activity of certain enzymes such as creatine kinase and a-hydroxybutyric dehydrogenase and ejection fraction has been demonstrated in patients with dilated cardiomyopathy.15 In the present study, a highly significant correlation was found between Na,K-pump concentration and LV systolic function estimated by ejection fraction, whereas a less significant correlation was observed between Na,Kpump concentration and LV diastolic function as estimated by LV end-diastolic volume. It has been demonstrated that 5 or more endomyocardial biopsy specimens provide a representative morphologic assessment of the condition of the rest of the myocardium,l6 and 3H-ouabain binding to endomyocardial biopsies taken from the same region showed a standard deviation of around XX&.* In the present study, a rather fixed position of the biopsy forceps in the apical portion of the LV during the sampling procedure ensured that the biopsies taken either for light microscopy or measurement of Na,K-pump concentration were rather homogenous. All our 24 patients had morphologic abnormalities compatible with dilated cardiomyopathy, although the LV function was normal in 5 patients. This allows a definite diagnosis of dilated cardiomyopathy in 19 patients. Three of the 5 patients with normal ventricular function had a history suggesting previous myocarditis. This is in good agreement with a spontaneous rise in ejection fraction and improvement in heart failure in approximately 40% of patients with previous myocarditis.17 According to earlier studies, there was no correlation either between morphologic changes estimated by volume fraction of collagen tissue and systolic or diastolic function of the LV,‘* or between volume fraction of collagen tissue and Na,K-pump concentration. This indicates that the decrease in Na,K-pump concentration with dilated cardiomyopathy is not the simple outcome of increased fibrosis in the myocardium. Acknowledgment: We wish to thank Torben Clausen for valuable discussion and Tove Lindahl Andersen and Susanne Olesen for expert technical assistance. 1. Skou JC. Enzymatic basis for active transport of Na’ and K’ across ceil membrane. Physiol Rev 1965;45:596-617. 2. Opie LH, Nathan II, Lubbe WF. Biochemical aspects of arrhythmogenesis and ventricular fibrillation. Am I Cardiol 1979:43:131-148. 3. Lee CO, Uhm’DY, Dresdner i. Sodium-calcium exchange in rabbit heart muscle cells: direct measurement of sarcoplasmic Ca2+ activity. Science
0.4-
1980:209:699-701. 0.2-
0.0 J 0
I 100
Concentration
1 200
I 300
1 400
of Na,K-pumps
500
(pmol/g
I 600
I 700
wet wt)
FIGURE 1. Relation between concentration of Na,K-pumps in biopsies and LV ejection fraction in patients with normal (0) and impaired ( l ) LV function.
4. Akera T. Brady TM. The role of Na.K-ATPase in the inotropic action of digitalis. Pharmacol Rev 1978;29:187-220, 5. Panagia V, Singh JN. Anand-Srivastava MB, Pierce GN, Jasmin G. Dhalla NS. Sarcolemmal alterations during the development of genetically determined cardiomyopathy. Cardiovasc Aes 1984;18:567-572. 6. Nargaard A, Baandrup U, Larsen JS. Kjeldsen K. Heart Na,K-ATPase activity in cordiomyopathic hamsters as estimated from K-dependent 3-OMFPase activity in crude homogenates. J Mel Cell Cordiol 1987:19:589-594. 7. Bajusz E. Baker JR, Nixon CW. Homburger F. Spontaneous, hereditary myocordial degeneration and congestive heart failure in a strain of Syrian hamsters. Ann NY Acad Sci 1969;156:105-129. 8. Nargaard A, Kjeldsen K, Hansen 0, Clausen T. Larsen CG. Larsen FG. Quantification of the 3H-ouabain binding site concentration in human myo-
June 1. 1988
cardium: a post mortem study. Cordiovasc Res 1986;26:428-435. 9. Greene DG. Carlise R, Grant C. Bunnell IL. Esimation of left ventricular volume by one-plane cineangiography. Circulation 1967;35:61-69. 10. Baandrup U, Olsen EGJ. Critical analysis of endomyocardial biopsies from patients suspected of having cardiomyopathy. I: Morphological and morphometric aspects. Br Heart J 1981;45:475-486. 11. Report of the WHO/ISCF task force on the definition and classification of cardiomyopathies. Br Heart J 1980;44:672-673. 12. Erdmann E, Brown L. The cardiac glycoside-receptor system in the human heart. Eur Heart f 1983;4(supp1A):61-65. 13. Kochsiek K. Increased therapeutic range, merely a pharmacokinetic problem. Basic Res Cardiol 1984:79:154-60. 14. Peters TJ. Wells G, Oakley CM, Brooksby AB, Jenkins BS. Webb-Peploe MM, Coltart IIJ. Enzymic analysis of endomyocardial biopsy specimens from patients with cardiomyopathies. Br Heart J 1977;39:1333-1339.
THE AMERICAN
JOURNAL
OF CARDIOLOGY
Volume 61
1315
15. Richardson PJ, Wodak AD, Atkinson L, Saunders JB, Jewitt DE. Relation between alcohol intake, myocardial enzyme activity, and myocardial function in dilated cardiomyopathy. Br Heart J 1986;56:165-170. 16. Baandrup U, Florio RA, Olsen EGJ. Do endomyocardial biopsies represent the morphology of the rest of the myocardium? A quantitative light microscopic study of single v. multiple biopsies with the King’s bioptome. Eur Heart J 1982;3:171-178. 17. Dee GW. Palacios IF, Fallon JT. Aretz HT, Mills J. Lee DCS. Johnson AJ. Active myocarditis in the spectrum of acute dilated cardiomyopathies. Clinical features, histologic correlates and clinical outcome. N Engl [ Med 1985;312:885-890. 18. Baandrup U. Florio RA, Rehahn M. Richardson PJ. Olsen EGJ. Critical analysis of endomyocardial biopsies from patients suspected of having cardiomyopathy. II: Comparison of histological and c1inical/haemadynamic information. Br Heart J 1981;45:487-493.
Relationof left VentricularFunctionand Na,K-Pump Concentrationin SuspectedIdiopathicDilated Cardiomyopathy AAGE NmGAARD, ULRIK BAANDRUP,
MD, JENS P. BAGGER, MD, PREBEN BJERREGAARD, MD, MD, KELD KJELDSEN, MD, and POUL E.B. THOMSEN, MD
highly significant (n = 24, r = 0.61, p
The possible relation between Na,K-pump concentration and left ventricular (LV) function was studied in 24 patients with suspected idiopathic dilated cardiomyopathy. This was done by measurement of SH-ouabain binding to biopsies obtained during ieftsided heart catheterization. in ail patients light microscopy of biopsies was compatible with dilated cardiomyopathy. Nineteen patients had impaired LV function as defined by NYHAIWHO and a Na,Kpump concentration of 331 f 19 pmoi/g wet weight, wheras 5 patients had normal LV function and a Na,K-pump concentration of 559 f 62 pmoi/ g wet weight (p
(Am J Cardioi 1968;61:1312-1315)
T
he Na,K-ATPase or Na,K-pump is of major importance in myocardial function. Thus, the active transport of Na and K across the cell membrane by the Na,K-pump is essential for excitability and contractility.l The reuptake by the Na,K-pump of K lost from the cell during the action potential prevents a possible arrhythmogenic rise of interstitial K.2 By maintaining the Na gradient across the cell membrane and associated Na-Ca exchange, the Na,K-pump plays a significant role in cellular Ca clearancee3 Finally, the Na,Kpump is accepted to be the cellular receptor for digitalFrom the Departments of Cardiology and Pathology, Aarhus Municipal Hospital, and Institute of Physiology, University of Aarhus, Denmark. This study was supported in part by the Danish Heart Foundation and the Danish Medical Research Council. Manuscript received October 1, 1987; revised manuscript received and accepted February 23,1988. Address for reprints: Aage Nergaard, MD, Department of Cardiology, Skejby Hospital, DK-8200 Aarhus N, Denmark.
1312
is glycosides.4 A decrease in Na,K-ATPase activity in the cardiac plasma membrane has been shown to be one of the earliest abnormalities during the course of hereditary cardiomyopathy in the hamster5r6 and it might be of importance in the associated intracellular Ca accumulation, mitochondrial calcification and cell necrosis.7 To our knowledge, the Na,K-pump has never been assessed in human cardiomyopathy. In this study, we investigated the concentration of Na,Kpumps in the left myocardium from patients suspected of dilated cardiomyopathy.
Methods Patients: The study was approved by the local ethics committee according to the Helsinki Declaration II. During a 2-year period (1985 to 19861,24 patients (12 men and 12 women, ages 25 to 62 years, mean 44) with suspected idiopathic dilated cardiomyopathy underwent a diagnostic left-sided heart catheterization. At the time of examination, 2 patients were treated with
June 1, 1988
digoxin, 14 with both digoxin and diuretics, and 8 with diuretics. All patients were normotensive. Serum potassium was in the normal range (3.5 to 5.0 mmol/liter). Heart catheterization: The left side of the heart was catheterized by way of the femoral artery. The left ventricular (LV) end-diastolic pressure was recorded. Biplane (18 patients] or single-plane (6) LV angiography and coronary arteriography were performed. Four endomycardial biopsies of 1 to 2 mg were taken from the apical portion of the LV wall using a Cordis biopsy forceps. Three of the biopsies were processed for light microscopy while the remaining 1 biopsy was frozen at -20°C until the determination of 3H-ouabain binding site concentration. 3H-ouabain binding: This assay was performed as previously described.8 Biopsy specimens were prewashed for 2 X 10 minutes at 0°C in a TRIS sucrose buffer (pH 7.3) containing 1 mmol/liter vanadate (NaVO& 3 mmol/liter MgS04, 10 mmol/liter TRIS chloride and 250 mmol/liter sucrose. Incubation took place in the TRIS sucrose buffer containing 1 X low6 mol/liter 3H-ouabain at 37'C for 2 X 60 minutes. This was followed by a wash at 0°C in unlabelled buffer for another 4 X 30 minutes to remove 3H-ouabain from the extracellular space. After blotting, the samples were weighed and 5% trichloroacetic acid was added. After extraction overnight and liquid scintillation counting, the amount of 3H-ouabain bound to the biopsies was calculated based on the specific activity of the incubation medium. After correcting for unspecific uptake in the presence of surplus of unlabelled ouabain, it was expressed as pmol/g wet weight of muscle tissue. Statistics: Ventricular volumes were determined from the angiography by the width-length method9 and expressed as ml/m2 of body surface area. The ejection fraction was defined as the ratio of angiographic stroke volume to end-diastolic volume. After elastic Van Gieson staining, the volume fraction of collagen tissue in the biopsies was assessed by point counting.lO Results are given as mean value f standard error of the mean. Statistical significance of any difference was determined using the &tailed t test for nonpaired groups of observations. Linear regression analysis was performed using the method of least squares. A p <0.05 was considered statistically significant.
Results Left-sided heart catheterization exposed neither congenital heart diseases, valvular diseases nor abnormalities in the coronary arteries. Nineteen patients had impaired LV function defined as LV end-diastolic volume 1100 ml/m2 and ejection fraction SO.45compatible with dilated cardiomyopathy.ll A history of heavy drinking was confirmed in 4 patients and 3 patients had a history suggesting previous myocarditis. Five patients had angiographically-determined normal LV function. No patient in this group had a history of drinking, whereas 3 patients had a history suggesting previous myocarditis. Light microscopy of LV biopsies from all 24 patients showed varying degrees of
THE AMERICAN
JOURNAL
OF CARDIOLOGY
1313
Volume 61
TABLE I Clinical Characteristics, Hemodynamic Parameters, Light Microscopy Findings and Na,K-Pump Concentration Normal LV Function (n = 5) 40 f II 8fl 61 f5 63 f 7.6 f 559 f
Age (~0 NYHA class LVEDP (mm Hg) LVEDV (ml/ms) EF (%) VFC (%) Na,K-pumps (pmollg wet weight)
4
5 3.9 62
Impaired LV Function (n = 19) 45 f 2 III-IV 23 f 2 140 f 14 31 f 2 5.1 f 0.6 331 f 19
p Value NS
EF = ejection fraction; NYHA class = New York Heart Association functional class; LV = left ventricle; LVEDP = left ventricular end-diastolic pressure; LVEDV = left ventricular end-diastolic volume; NS = not significant (p 20.05): VFC = volume fraction of collagen.
TABLE II Correlation Matrix of Hemodynamic Parameters, Microscopy Findings and Na,K-Pump Concentration
Age LVEDP LVEDV EF VFC Na,K-pumps
Age
LVEDP
LVEDV
EF
1.00 0.05 -0.18 -0.10 -0.40 -0.20
1.00 0.47’ -0.61’ -0.10 -0.37
1.00 -0.59’ 0.13 -0.49’
1.00 0.06 0.81’
VFC
1 .oo -0.08
Light
Na,K-Pumps
1 .oo
* p <0.05. EF = ejection fraction; LVEDP = left ventricular end-diastolic pressure; LVEDV = left ventricular end-diastolic volume: VFC = volume fraction of collagen.
nuclear hypertrophy, fiber attenuation, smooth-muscle cell hypertrophy or fibrosis compatible with dilated cardiomyopathy.1° The degree of fibrosis was evaluated by measurement of volume fraction of collagen tissue in the biopsies, The Na,K-pump concentration was determined in the LV biopsies by measuring 3Houabain binding. The clinical characteristics, hemodynamic parameters, light microscopy findings and Na,K-pump concentration in patients with normal and impaired LV function, respectively, are listed in Table I. Table II lists the correlation coefficients between the hemodynamic parameters, light microscopy findings and Na,K-pump concentration in all 24 patients. The correlations between diastolic LV function estimated by LV end-diastolic pressure or estimated by LV end-diastolic volume and Na,K-pump concentration were not significant and only weakly significant, respectively. As can be seen in Figure 1, there was a highly significant correlation between Na,K-pump concentration and systolic function of LV, as estimated by ejection fraction in all 24 patients. Separate correlation analysis between Na,K-pump concentration and ejection fraction in the 16 patients receiving digoxin and in the 8 patients taking diuretics alone also showed significance (r = 0.69, p <0.005 and r = 0.89, p <0.005, respectively). There were no correlations between the
1314
HEART Na,K-PUMPS
AND DILATED
CARDIOMYOPATHY
volume fraction of collagen tissue and the hemodynamic parameters or the Na,K-pump concentration in all 24 patients (Table II).
Discussion The Na,K-pump in the human myocardium has only been assessedin very few studies8,12and, to our knowledge, never in cardiomyopathic patients. The present study demonstrates a decrease in 3H-ouabain binding site concentration with dilated cardiomyopathy. This might be assumed to represent a decrease in Na,K-pump concentration because 3H-ouabain binding to endomyocardial biopsies has proved adequate for assessment of Na,K-pumps in the human myocardium.8 During digoxin treatment a tissue concentration of approximately 75 pmollg wet weight has been found in the myocardium. l3 This might interfere with 3Houabain binding at receptor level. However, separate correlation analyses between Na,K-pump concentration and ejection fraction in patients receiving digoxin or diuretics alone showed significance, which indicates that the decrease in Na,K-pump concentration with impaired LV function is not the simple outcome of digoxin treatment. In hamster hereditary cardiomyopathy, the progression of cardiac damage is associated with intracellular Ca accumulation followed by cell necrosis, congestive heart failure and ultimately death.7 In human dilated cardiomyopathy, calcification is not a characteristic finding,‘0 whereas changes in several myocardial enzymes have been demonstrated. Thus, endomyocardial biopsies of the LV in patients with dilated cardiomyopathy showed a decrease in myofibrillar Ca-ATPase and activity of several mitochondrial en1.0 r =
0.81
p < 0.001 n = 24
1
0.8
0 i
g 3
O.%-
References
s tt: fz 3
$ .C) w
zymes.14In hypertrophic cardiomyopathy these enzymatic activities were normal. Furthermore, a correlation between the activity of certain enzymes such as creatine kinase and a-hydroxybutyric dehydrogenase and ejection fraction has been demonstrated in patients with dilated cardiomyopathy.15 In the present study, a highly significant correlation was found between Na,K-pump concentration and LV systolic function estimated by ejection fraction, whereas a less significant correlation was observed between Na,Kpump concentration and LV diastolic function as estimated by LV end-diastolic volume. It has been demonstrated that 5 or more endomyocardial biopsy specimens provide a representative morphologic assessment of the condition of the rest of the myocardium,l6 and 3H-ouabain binding to endomyocardial biopsies taken from the same region showed a standard deviation of around XX&.* In the present study, a rather fixed position of the biopsy forceps in the apical portion of the LV during the sampling procedure ensured that the biopsies taken either for light microscopy or measurement of Na,K-pump concentration were rather homogenous. All our 24 patients had morphologic abnormalities compatible with dilated cardiomyopathy, although the LV function was normal in 5 patients. This allows a definite diagnosis of dilated cardiomyopathy in 19 patients. Three of the 5 patients with normal ventricular function had a history suggesting previous myocarditis. This is in good agreement with a spontaneous rise in ejection fraction and improvement in heart failure in approximately 40% of patients with previous myocarditis.17 According to earlier studies, there was no correlation either between morphologic changes estimated by volume fraction of collagen tissue and systolic or diastolic function of the LV,‘* or between volume fraction of collagen tissue and Na,K-pump concentration. This indicates that the decrease in Na,K-pump concentration with dilated cardiomyopathy is not the simple outcome of increased fibrosis in the myocardium. Acknowledgment: We wish to thank Torben Clausen for valuable discussion and Tove Lindahl Andersen and Susanne Olesen for expert technical assistance. 1. Skou JC. Enzymatic basis for active transport of Na’ and K’ across ceil membrane. Physiol Rev 1965;45:596-617. 2. Opie LH, Nathan II, Lubbe WF. Biochemical aspects of arrhythmogenesis and ventricular fibrillation. Am I Cardiol 1979:43:131-148. 3. Lee CO, Uhm’DY, Dresdner i. Sodium-calcium exchange in rabbit heart muscle cells: direct measurement of sarcoplasmic Ca2+ activity. Science
0.4-
1980:209:699-701. 0.2-
0.0 J 0
I 100
Concentration
1 200
I 300
1 400
of Na,K-pumps
500
(pmol/g
I 600
I 700
wet wt)
FIGURE 1. Relation between concentration of Na,K-pumps in biopsies and LV ejection fraction in patients with normal (0) and impaired ( l ) LV function.
4. Akera T. Brady TM. The role of Na.K-ATPase in the inotropic action of digitalis. Pharmacol Rev 1978;29:187-220, 5. Panagia V, Singh JN. Anand-Srivastava MB, Pierce GN, Jasmin G. Dhalla NS. Sarcolemmal alterations during the development of genetically determined cardiomyopathy. Cardiovasc Aes 1984;18:567-572. 6. Nargaard A, Baandrup U, Larsen JS. Kjeldsen K. Heart Na,K-ATPase activity in cordiomyopathic hamsters as estimated from K-dependent 3-OMFPase activity in crude homogenates. J Mel Cell Cordiol 1987:19:589-594. 7. Bajusz E. Baker JR, Nixon CW. Homburger F. Spontaneous, hereditary myocordial degeneration and congestive heart failure in a strain of Syrian hamsters. Ann NY Acad Sci 1969;156:105-129. 8. Nargaard A, Kjeldsen K, Hansen 0, Clausen T. Larsen CG. Larsen FG. Quantification of the 3H-ouabain binding site concentration in human myo-
June 1. 1988
cardium: a post mortem study. Cordiovasc Res 1986;26:428-435. 9. Greene DG. Carlise R, Grant C. Bunnell IL. Esimation of left ventricular volume by one-plane cineangiography. Circulation 1967;35:61-69. 10. Baandrup U, Olsen EGJ. Critical analysis of endomyocardial biopsies from patients suspected of having cardiomyopathy. I: Morphological and morphometric aspects. Br Heart J 1981;45:475-486. 11. Report of the WHO/ISCF task force on the definition and classification of cardiomyopathies. Br Heart J 1980;44:672-673. 12. Erdmann E, Brown L. The cardiac glycoside-receptor system in the human heart. Eur Heart f 1983;4(supp1A):61-65. 13. Kochsiek K. Increased therapeutic range, merely a pharmacokinetic problem. Basic Res Cardiol 1984:79:154-60. 14. Peters TJ. Wells G, Oakley CM, Brooksby AB, Jenkins BS. Webb-Peploe MM, Coltart IIJ. Enzymic analysis of endomyocardial biopsy specimens from patients with cardiomyopathies. Br Heart J 1977;39:1333-1339.
THE AMERICAN
JOURNAL
OF CARDIOLOGY
Volume 61
1315
15. Richardson PJ, Wodak AD, Atkinson L, Saunders JB, Jewitt DE. Relation between alcohol intake, myocardial enzyme activity, and myocardial function in dilated cardiomyopathy. Br Heart J 1986;56:165-170. 16. Baandrup U, Florio RA, Olsen EGJ. Do endomyocardial biopsies represent the morphology of the rest of the myocardium? A quantitative light microscopic study of single v. multiple biopsies with the King’s bioptome. Eur Heart J 1982;3:171-178. 17. Dee GW. Palacios IF, Fallon JT. Aretz HT, Mills J. Lee DCS. Johnson AJ. Active myocarditis in the spectrum of acute dilated cardiomyopathies. Clinical features, histologic correlates and clinical outcome. N Engl [ Med 1985;312:885-890. 18. Baandrup U. Florio RA, Rehahn M. Richardson PJ. Olsen EGJ. Critical analysis of endomyocardial biopsies from patients suspected of having cardiomyopathy. II: Comparison of histological and c1inical/haemadynamic information. Br Heart J 1981;45:487-493.