Effects of Electrical Countershock Creatine Phosphokinase
ALI EHSANI,
MD
GORDON
A. EWY,
BURTON
E. SOBEL,
MD, MD,
FACC FACC
St. Louis, Missouri
From the Cardiovascular Division, Washington University. St. Louis, MO. This work was supported in part by U. S. Public Health Service MIRU Contract PH 43-68 NHLI 1332 (University of California, San Diego) and NIH SCOR in Ischemit Heart Disease HL 16705 (Washington University, St. Louis). Manuscript accepted April 30, 1975. Address for reprints: Burton E. Sobel, MD, Cardiovascular Division, Washington University, 660 South Euclid, St. Louis, MO. 63 1 IO.
12
January 1976
on Serum
(CPK) lsoenzyme
Activity
Total and MB serum creatine phosphokinase (CPK) activity levels were measured serially in 30 patients treated with direct current electrical countershock, 17 patients with acute myocardial infarction and 25 normal subjects. In addition, serial determinations of total and MB CPK in serum were performed in 11 closed chest anesthetized dogs subjected to 10 repetitive countershocks at 15 second intervals with a delivered energy of 240 joules per countershock. Less than 4 milli-international units (mlU)/ml of MB CPK was found in the serum of normal subjects. Patients with myocardial infarction whose elevated total CPK levels were comparable with those of patients treated with cardioversion had a substantial rise in MB CPK activity, with peak values averaging 39 f 6 mlU/ml (mean f standard error). Fifteen of the 30 patients treated with countershock had elevated total CPK activity that peaked within 4 hours. In this group, MM CPK elevations accounted for the overall rise in CPK activity. In two patients, modest elevations of MB CPK (11 and 13 mlU/ml, respectively) were observed after cardioversion. In all 11 dogs total CPK increased after countershock, peaking to 1,666 f 410 mlU/ml within 6 hours. Six dogs had increased MB CPK activity (52 f 6 mlU/ml) and myocardial necrosis demonstrable histologically 4 days later. The results indicate that (1) myocardial damage in dogs produced by intense, repetitive countershock is associated with increased serum MB CPK; and (2) countershock as conventionally used in patients does not generally produce myocardial damage and serum MB CPK elevation. Although release of MB CPK into serum occasionally occurs after countershock, perhaps reflecting myocardial damage, the elevations appear to be modest. Thus, electrical countershock does not obscure the diagnosis .of myocardial infarction or impair quantitative assessment of the extent of myocardial damage based on analysis of serum MB CPK activity.
Electrical cardioversion with direct current countershock is frequently required for treatment of tachyarrhythmias or ventricular fibrillation in patients with suspected or evolving myocardial infarction. Under standardized conditions, direct current countershock may produce myocardial necrosis in experimental animals.’ It is known to alter S-T segments and T waves in the electrocardiogram and to increase the activity of several serum enzymes in patients.2-6 These changes may suggest myocardial damage, and lead to the false positive diagnosis of myocardial infarction or obscure its recognition. Assessment of myocardial infarction has been facilitated by determination of total serum creatine phosphokinase (CPK) activity and recently by assay of activity of MB CPK, an isoenzyme relatively specific to myocardium. MB CPK activity is elevated consistently in serum after acute myocardial infarction7 Furthermore, since the only human tissue containing appreciable amounts of this isoenzyme is
The American Journal of CARDIOLOGY
Volume 37
CARDIOVERSION
myocardium, insults to organs other than the heart fail to increase serum MB CPK despite substantial elevations of total CPK activity.8 Since MB CPK appears to be quite specific to human myocardium, it is particularly useful in detecting and quantitatively assessing myocardial necrosis or infarction. In addition, the absence of MB CPK from human skeletal muscle9 makes it possible to determine whether myocardium or skeletal muscle is the source of serum CPK elevations under specific circumstances. Accordingly, this study was undertaken to determine (1) whether direct current countershock leads to increased serum MB CPK in patients and experimental animals, and (2) whether serum CPK elevations after electrical cardioversion reflect release of enzyme from skeletal muscle or myocardium, or both. Serial determinations of MB and total CPK activity were performed in serum samples from 30 patients without suspected myocardial infarction after direct current countershock required for treatment of tachyarrhythmias. In addition, the activity levels of serum total and MB CPK were determined serially in 25 normal subjects and 17 patients with acute myocardial infarction selected on the basis of elevations of total CPK activity comparable with those occurring in some patients treated with countershock. Parallel studies were performed in 11 closed chest, anesthetized dogs whose hearts were analyzed morphologically as well. The purpose of elucidating the source of elevated serum CPK activity in patients treated with direct current countershock was to facilitate accurate diagnosis of myocardial infarction, even when electrical cardioversion is required, and to determine whether direct current countershock damages myocardium in patients as it does under experimental conditions in which multiple high energy discharges are applied to closed chest animals. Methods Patients Studied
Thirty patients, 35 to 80 years of age (average 54 years), without suspected myocardial infarction but requiring direct current countershock for treatment of various tachyarrhythmias, were studied. Patients with signs or symptoms suggestive of acute myocardial infarction or shock or those with a history of recent myocardial infarction (within 2 years) or musculoskeletal disorders were excluded. Twenty-three patients had atria1 fibrillation, five had atria1 flutter, and two had paroxysmal supraventricular tachycardia. Electrical countershock was performed using an American Optical or Physio Control Life Pack cardioverter after intravenous administration of diazepam or sodium methohexital. The American Optical unit used delivered approximately 75 percent and the Physio Control Life Pack unit approximately 90 percent of the indicated energy when discharged into an artificial load of 50 ohms. Anterior and posterior paddles were used after liberal application of Reduxe paste. The total cumulated energy required ranged between 40 and 750 watt-seconds (joules). Repetitive shocks were required in 70 percent of the patients. In addition, total CPK activity and its isoenzyme profile were as-
January
AND MB CPK-EHSANI
ET AL
sayed in sera from 25 normal subjects. MB CPK activity was determined in serum samples from an additional group of I7 patients with acute myocardial infarction, selected on the basis of total peak CPK activity comparable with peak values in patients treated with countershock. Biochemical
Procedures
Blood samples were obtained through an intravenous heparin lock before, immediately after and serially for 24 hours after electrical countershock. To define the pattern of CPK elevation, samples were obtained hourly in the first eight patients studied. Since peak CPK activity occurred consistently within the first 4 hours, in the remaining patients samples were obtained less frequently, that is, every 2 to 4 hours. Blood samples were assayed for CPK activity as follows: Each sample was immediately placed in 10 millimolar ethyleneglycoltetraacetic acid (EGTA) and centrifuged at 7,500 g for 10 minutes at 4°C. The plasma was removed, fast-frozen in dry ice and alcohol, and stored for a maximum of 96 hours in a -20°C freezer. Before assay, samples were thawed rapidly under tap water. CPK activity was assayed spectrophotometrically at 30°C by the Rosalki method.‘O When necessary, samples were diluted with 0.01 molar Tris hydrochloride pH 7.4, with 0.1 percent bovine serum albumin. MB CPK activity in serum was assayed with a quantitative procedure recently described in detail.‘l Briefly, CPK isoenzymes were separated by cellulose acetate electrophoresis in 1 millimolar EGTA, Tris-barbital, pH 8.8, at 250 volts for 65 minutes at 4’C. I2 Activity of the individual isoenzymes was assayed fluorometrically by immersing the region of the cellulose acetate membrane containing each isoenzyme in aqueous medium and kinetically measuring the nicotine adenine dinucleotide phosphate, reduced form (NADPH), generated.l’ Extracts of fresh human and canine tissue obtained at operation were prepared as previously described and analyzed for total CPK and CPK isoenzyme activity with the same quantitative assay procedure.8*g Animal Studies To determine whether myocardial injury induced by intense repetitive direct current countershock is associated with increased serum MB CPK activity, 11 mongrel dogs weighing 16.5 to 25 kg were anesthetized with sodium pentobarbital, 30 mg/kg intravenously, and subjected to 10 repetitive electrical countershocks at 15 second intervals using paddle electrodes 8 cm in diameter. The delivered energy across a 50 ohm resistance was approximately 240 joules per countershock. Serum samples were obtained and analyzed in the same fashion as in the studies of patients. The dogs were killed 4 days after electrical countershock and the hearts examined grossly and microscopically to evaluate the extent of myocardial damage. The extent of necrosis in each heart was quantified as previously described by taking into account the gross area of discoloration and the severity of injury graded microscopically.lJ3 Results
Serum CPK and MB CPK activity in patients: As shown in Figure 1, normal subjects without cardiovascular disease had virtually no MB CPK activity in serum (less than 5 mIU/ml).ll Patients with acute myocardial infarction with modest elevations of total CPK activity comparable with those seen
1976
The American
Journal
of CARDIOLOGY
Volume
37
13
CARDIOVERSION
AND MB CPK-EHSANI
ET AL.
TABLE
I
Delivered
Energy and CPK Activity
After
Cardioversion
DC Shock (joules)*
0
n
Total
CPK
Case “0.
.
MB CPK
:
I
::. L . .
I
4.
l-7 o’--
Acute DC C:ountershock Myocardial n=30 Infarction n=17 FIGURE 1. Total and MB CPK activity in serum from normal subjects, patients with acute myocardial infarction and patients treated with direct current (DC) countershock. Bars and vertical slashes indicate mean CPK activity f standard error. Substantial serum MB CPK activity was seen in patients with acute myocardial infarction compared with patients treated by direct current electrical shock. No Cardiovascular Disease n=25
240
-200 z 2 z 160 : 2
120
2 2
8C
z z,
4c
I
-Total --MB
_--o--+4_*__
C
I
I
__ I
I
I
CPK CPK
_‘--0‘-‘_*__ I
8
I
I
.
1+ 2 4 6 8 10 12 14 16 18 20 22 24 TIME AFTER COUNTERSHOCK (Hours) FIGURE 2. The pattern of total and MB serum CPK elevations after direct current countershock in a typical patient. Total CPK activity peaked within 4 hours. An unexplained second peak (seen in two patients) occurred several hours later. MB CPK peaked almost simultaneously with total CPK.
14
January 1976
3 4 5 6
42 35
i 9 10 11
i&”
. .
The American Journal of CARDIOLOGY
Age (vrl
12 I3 14 15 I6 I7 I8 I9 20 21 22 23 24 25 26 27 28
iz
:; 58 75 41 71 47 58 4588 48 44 58 42 72 53 68 62 45 38 42 67
Rhythm AF AF PSVT AFI AF AFI AF AFI AF AFI AF AF AF AF AF AF AF AF AF AF AF AF AF AF’ PSVT AF AFI AF AF AF
Dial Setting 300 750 40 185 350 50 205 37550 175 100 50 400 675 150 600 25 500 250 150 575 485 60 75 50 200 85 150 300 150
Delivered Energy 209 524 29 132 245 37 181 55 245
(I) (3) (1) (1) (2) (2) (2) (2) (2)
‘Z 45 275 618 107 417 18 352 176 135 402 437 51 69 45
I?; (2) (1) (3) (I) (3) (1) (2) (I) (II (3) (2) (1) (1) (2)
‘% 135 273 135
I:; (I) (2) (1)
Peak CPK
MB CPK
‘“,‘iY’
milt (miU’
297 222 18 91 33 47 59 81 505 28 IO 144 479 252 47 27 36 34 27 206 57 564 135 9 34 I8 29 26
N 13 N N N N N N N N N N N N N N N N N N N 11 N N N N N N N N
;z
“Total cumulated energy (number of shocks times intensity).’ The number of shocks is indicated in parentheses. tValues of MB CPK activity
ALI EHSANI,
MD
GORDON
A. EWY,
BURTON
E. SOBEL,
MD, MD,
FACC FACC
St. Louis, Missouri
From the Cardiovascular Division, Washington University. St. Louis, MO. This work was supported in part by U. S. Public Health Service MIRU Contract PH 43-68 NHLI 1332 (University of California, San Diego) and NIH SCOR in Ischemit Heart Disease HL 16705 (Washington University, St. Louis). Manuscript accepted April 30, 1975. Address for reprints: Burton E. Sobel, MD, Cardiovascular Division, Washington University, 660 South Euclid, St. Louis, MO. 63 1 IO.
12
January 1976
on Serum
(CPK) lsoenzyme
Activity
Total and MB serum creatine phosphokinase (CPK) activity levels were measured serially in 30 patients treated with direct current electrical countershock, 17 patients with acute myocardial infarction and 25 normal subjects. In addition, serial determinations of total and MB CPK in serum were performed in 11 closed chest anesthetized dogs subjected to 10 repetitive countershocks at 15 second intervals with a delivered energy of 240 joules per countershock. Less than 4 milli-international units (mlU)/ml of MB CPK was found in the serum of normal subjects. Patients with myocardial infarction whose elevated total CPK levels were comparable with those of patients treated with cardioversion had a substantial rise in MB CPK activity, with peak values averaging 39 f 6 mlU/ml (mean f standard error). Fifteen of the 30 patients treated with countershock had elevated total CPK activity that peaked within 4 hours. In this group, MM CPK elevations accounted for the overall rise in CPK activity. In two patients, modest elevations of MB CPK (11 and 13 mlU/ml, respectively) were observed after cardioversion. In all 11 dogs total CPK increased after countershock, peaking to 1,666 f 410 mlU/ml within 6 hours. Six dogs had increased MB CPK activity (52 f 6 mlU/ml) and myocardial necrosis demonstrable histologically 4 days later. The results indicate that (1) myocardial damage in dogs produced by intense, repetitive countershock is associated with increased serum MB CPK; and (2) countershock as conventionally used in patients does not generally produce myocardial damage and serum MB CPK elevation. Although release of MB CPK into serum occasionally occurs after countershock, perhaps reflecting myocardial damage, the elevations appear to be modest. Thus, electrical countershock does not obscure the diagnosis .of myocardial infarction or impair quantitative assessment of the extent of myocardial damage based on analysis of serum MB CPK activity.
Electrical cardioversion with direct current countershock is frequently required for treatment of tachyarrhythmias or ventricular fibrillation in patients with suspected or evolving myocardial infarction. Under standardized conditions, direct current countershock may produce myocardial necrosis in experimental animals.’ It is known to alter S-T segments and T waves in the electrocardiogram and to increase the activity of several serum enzymes in patients.2-6 These changes may suggest myocardial damage, and lead to the false positive diagnosis of myocardial infarction or obscure its recognition. Assessment of myocardial infarction has been facilitated by determination of total serum creatine phosphokinase (CPK) activity and recently by assay of activity of MB CPK, an isoenzyme relatively specific to myocardium. MB CPK activity is elevated consistently in serum after acute myocardial infarction7 Furthermore, since the only human tissue containing appreciable amounts of this isoenzyme is
The American Journal of CARDIOLOGY
Volume 37
CARDIOVERSION
myocardium, insults to organs other than the heart fail to increase serum MB CPK despite substantial elevations of total CPK activity.8 Since MB CPK appears to be quite specific to human myocardium, it is particularly useful in detecting and quantitatively assessing myocardial necrosis or infarction. In addition, the absence of MB CPK from human skeletal muscle9 makes it possible to determine whether myocardium or skeletal muscle is the source of serum CPK elevations under specific circumstances. Accordingly, this study was undertaken to determine (1) whether direct current countershock leads to increased serum MB CPK in patients and experimental animals, and (2) whether serum CPK elevations after electrical cardioversion reflect release of enzyme from skeletal muscle or myocardium, or both. Serial determinations of MB and total CPK activity were performed in serum samples from 30 patients without suspected myocardial infarction after direct current countershock required for treatment of tachyarrhythmias. In addition, the activity levels of serum total and MB CPK were determined serially in 25 normal subjects and 17 patients with acute myocardial infarction selected on the basis of elevations of total CPK activity comparable with those occurring in some patients treated with countershock. Parallel studies were performed in 11 closed chest, anesthetized dogs whose hearts were analyzed morphologically as well. The purpose of elucidating the source of elevated serum CPK activity in patients treated with direct current countershock was to facilitate accurate diagnosis of myocardial infarction, even when electrical cardioversion is required, and to determine whether direct current countershock damages myocardium in patients as it does under experimental conditions in which multiple high energy discharges are applied to closed chest animals. Methods Patients Studied
Thirty patients, 35 to 80 years of age (average 54 years), without suspected myocardial infarction but requiring direct current countershock for treatment of various tachyarrhythmias, were studied. Patients with signs or symptoms suggestive of acute myocardial infarction or shock or those with a history of recent myocardial infarction (within 2 years) or musculoskeletal disorders were excluded. Twenty-three patients had atria1 fibrillation, five had atria1 flutter, and two had paroxysmal supraventricular tachycardia. Electrical countershock was performed using an American Optical or Physio Control Life Pack cardioverter after intravenous administration of diazepam or sodium methohexital. The American Optical unit used delivered approximately 75 percent and the Physio Control Life Pack unit approximately 90 percent of the indicated energy when discharged into an artificial load of 50 ohms. Anterior and posterior paddles were used after liberal application of Reduxe paste. The total cumulated energy required ranged between 40 and 750 watt-seconds (joules). Repetitive shocks were required in 70 percent of the patients. In addition, total CPK activity and its isoenzyme profile were as-
January
AND MB CPK-EHSANI
ET AL
sayed in sera from 25 normal subjects. MB CPK activity was determined in serum samples from an additional group of I7 patients with acute myocardial infarction, selected on the basis of total peak CPK activity comparable with peak values in patients treated with countershock. Biochemical
Procedures
Blood samples were obtained through an intravenous heparin lock before, immediately after and serially for 24 hours after electrical countershock. To define the pattern of CPK elevation, samples were obtained hourly in the first eight patients studied. Since peak CPK activity occurred consistently within the first 4 hours, in the remaining patients samples were obtained less frequently, that is, every 2 to 4 hours. Blood samples were assayed for CPK activity as follows: Each sample was immediately placed in 10 millimolar ethyleneglycoltetraacetic acid (EGTA) and centrifuged at 7,500 g for 10 minutes at 4°C. The plasma was removed, fast-frozen in dry ice and alcohol, and stored for a maximum of 96 hours in a -20°C freezer. Before assay, samples were thawed rapidly under tap water. CPK activity was assayed spectrophotometrically at 30°C by the Rosalki method.‘O When necessary, samples were diluted with 0.01 molar Tris hydrochloride pH 7.4, with 0.1 percent bovine serum albumin. MB CPK activity in serum was assayed with a quantitative procedure recently described in detail.‘l Briefly, CPK isoenzymes were separated by cellulose acetate electrophoresis in 1 millimolar EGTA, Tris-barbital, pH 8.8, at 250 volts for 65 minutes at 4’C. I2 Activity of the individual isoenzymes was assayed fluorometrically by immersing the region of the cellulose acetate membrane containing each isoenzyme in aqueous medium and kinetically measuring the nicotine adenine dinucleotide phosphate, reduced form (NADPH), generated.l’ Extracts of fresh human and canine tissue obtained at operation were prepared as previously described and analyzed for total CPK and CPK isoenzyme activity with the same quantitative assay procedure.8*g Animal Studies To determine whether myocardial injury induced by intense repetitive direct current countershock is associated with increased serum MB CPK activity, 11 mongrel dogs weighing 16.5 to 25 kg were anesthetized with sodium pentobarbital, 30 mg/kg intravenously, and subjected to 10 repetitive electrical countershocks at 15 second intervals using paddle electrodes 8 cm in diameter. The delivered energy across a 50 ohm resistance was approximately 240 joules per countershock. Serum samples were obtained and analyzed in the same fashion as in the studies of patients. The dogs were killed 4 days after electrical countershock and the hearts examined grossly and microscopically to evaluate the extent of myocardial damage. The extent of necrosis in each heart was quantified as previously described by taking into account the gross area of discoloration and the severity of injury graded microscopically.lJ3 Results
Serum CPK and MB CPK activity in patients: As shown in Figure 1, normal subjects without cardiovascular disease had virtually no MB CPK activity in serum (less than 5 mIU/ml).ll Patients with acute myocardial infarction with modest elevations of total CPK activity comparable with those seen
1976
The American
Journal
of CARDIOLOGY
Volume
37
13
CARDIOVERSION
AND MB CPK-EHSANI
ET AL.
TABLE
I
Delivered
Energy and CPK Activity
After
Cardioversion
DC Shock (joules)*
0
n
Total
CPK
Case “0.
.
MB CPK
:
I
::. L . .
I
4.
l-7 o’--
Acute DC C:ountershock Myocardial n=30 Infarction n=17 FIGURE 1. Total and MB CPK activity in serum from normal subjects, patients with acute myocardial infarction and patients treated with direct current (DC) countershock. Bars and vertical slashes indicate mean CPK activity f standard error. Substantial serum MB CPK activity was seen in patients with acute myocardial infarction compared with patients treated by direct current electrical shock. No Cardiovascular Disease n=25
240
-200 z 2 z 160 : 2
120
2 2
8C
z z,
4c
I
-Total --MB
_--o--+4_*__
C
I
I
__ I
I
I
CPK CPK
_‘--0‘-‘_*__ I
8
I
I
.
1+ 2 4 6 8 10 12 14 16 18 20 22 24 TIME AFTER COUNTERSHOCK (Hours) FIGURE 2. The pattern of total and MB serum CPK elevations after direct current countershock in a typical patient. Total CPK activity peaked within 4 hours. An unexplained second peak (seen in two patients) occurred several hours later. MB CPK peaked almost simultaneously with total CPK.
14
January 1976
3 4 5 6
42 35
i 9 10 11
i&”
. .
The American Journal of CARDIOLOGY
Age (vrl
12 I3 14 15 I6 I7 I8 I9 20 21 22 23 24 25 26 27 28
iz
:; 58 75 41 71 47 58 4588 48 44 58 42 72 53 68 62 45 38 42 67
Rhythm AF AF PSVT AFI AF AFI AF AFI AF AFI AF AF AF AF AF AF AF AF AF AF AF AF AF AF’ PSVT AF AFI AF AF AF
Dial Setting 300 750 40 185 350 50 205 37550 175 100 50 400 675 150 600 25 500 250 150 575 485 60 75 50 200 85 150 300 150
Delivered Energy 209 524 29 132 245 37 181 55 245
(I) (3) (1) (1) (2) (2) (2) (2) (2)
‘Z 45 275 618 107 417 18 352 176 135 402 437 51 69 45
I?; (2) (1) (3) (I) (3) (1) (2) (I) (II (3) (2) (1) (1) (2)
‘% 135 273 135
I:; (I) (2) (1)
Peak CPK
MB CPK
‘“,‘iY’
milt (miU’
297 222 18 91 33 47 59 81 505 28 IO 144 479 252 47 27 36 34 27 206 57 564 135 9 34 I8 29 26
N 13 N N N N N N N N N N N N N N N N N N N 11 N N N N N N N N
;z
“Total cumulated energy (number of shocks times intensity).’ The number of shocks is indicated in parentheses. tValues of MB CPK activity
