LETTERS TO THE EDITOR
VECTORCARDIOGRAPHY AND BODY SURFACE ISOPOTENTlAL MAPPING TO DETECT OLD MYOCARDIAL INFARCTION
TABLE I (Atkins et al.) One Year Follow-Up of Patients Who Had Third Degree A-V Block With Complete Right Bundle Branch Block Plus Left Anterior Hemiblock During Acute Myocardial Infarction Unpaced (no.) Ref
Patients
Deaths
3
:
5
z
2
06
6,7 21 Amikam and Riss Total
6
:
Paced (no.) Patients 0 7
1’2 2
I;:
0 41
: 21f51%)
: 26
Deaths :
0 2 8 1 3(12%)
A-V = atrioventricular; Ref = reference number.
Because our study was retrospective and unrandomized, the conclusion is not as strong scientifically as we and others would like. However, our statement that further randomized studies of patients in the group seem unjustified was based not only on the clear-cut difference in long-term prognosis in our series but also took into account the difficulties of attempting to assemble a randomized series. A case load of 500 acute myocardial infarctions per year would be likely to produce 25 patients with right bundle branch block plus left anterior hemiblock. Eleven of these 25 patients would manifest transient third degree A-V block and, of the 11 with such block, 5 would die in the hospital of pump failure, leaving 6 patients per year for randomization. Hence, to randomize enough patients to have 30 in each group would require 10 years. We believed it unjustified to initiate a study to randomize when the odds of obtaining scientifically valid information in a reasonable period of timeare nil and the principal reason for restraint is the expense of a pacemaker. A large multicenter trial to randomize patients may be justified because data on a substantial number of patients could be obtained in a reasonable amount of time and resolve this important problem. James M. Atkins, MD, FACC C. Gunnar Blomqvist, MD, FACC Charles 8. Mullins, MD, FACC Department of Internal Medicine The University of Texas Health Science Center Dallas, Texas
I enjoyed immensely the report by Vincent et al.’ on the contribution of body surface isopotential mapping to the diagnosis of old inferior myocardial infarction. Techniques useful in this diagnosis are of great practical import because QS or QR acute patterns of inferior leads in the standard electrocardiogram are often replaced by nondiagnostic qR or rS patterns. Vectorcardiography has also been found useful in detecting old inferior myocardial infarction in the absence of diagnostic Q waves in the inferior leads of the standard electrocardiogram. In addition, even inferior infarcts producing early inferiorly oriented forces and resulting in rS patterns in leads III and aVF have not escaped diagnosis by vectorcardiography. If the authors have recorded vectorcardiograms in their patients, I would be interested in the characteristics of the QRS loops of the frontal plane, particularly in their patients exemplified by Figures 5 and 6, who did not display diagnostic features of inferior myocardial infarction in the 12 lead electrocardiogram. John E. Madias, MD Cardiology Division Boston City Hospital Boston, Massachusetts References 1. Vlnconl GM. Ablldrkov JA, Burgen MJ, at ak Diagnosis of old inferior myocardial infarctlon bv bodv surface isowtential man&w. Am J Cardlol 39:510-515. 1977 2. LovIne H6, Vo&g E, Wlllla~r RA: Ele&&rdlogram and vectorcardiogram in myocardiil infarction. Circulation 45:457-470. 1972
REPLY
Although we recorded vectorcardiograms in some of our patients, the sampling is incomplete and the information not suitable for formal analysis. Vectorcardiography certainly seems to be superior to scalar electrocardiography in the diagnosis of previous inferior wall infarction. Sohi et al.’ have reported that the body surface map is superior to the scalar electrocardiogram and vectorcardiogram in detecting patients with previous infarction or severe coronary artery disease. Further comparison of body surface map data with vectorcardiographic data is necessary to establish the role of each of these procedures in the diagnosis of previous infarction. G. Michael Vincent, MD, FACC Department of Internal Medicine Alds Hospital Salt Lake City, Utah
References 1. ah*8 WR, Sutton R, Oh W, et al: Long-term prognosls after acute anterior infarction with atrloventrlcular block. Sr Marl J 39:198-199.1977 2. NlmotrAA,Shwoolu 85 Jr, Hullor AM Jr, et ak Slgnlfkxnce of bundle branch block during acute myocardtal lnfarctlon. Am Heart J 90~439-444, 1975 3. ScanIon PJ, Pryor R, I)lounl SQ h: Right bundle-branch block associated with left sup&or or Inferior lntraventrlcular block: associated with acute myocardlal InfarctIon. Clrculatlon 42:1135-1142. 1970 4. Wau# RA, Wm 08, Hw TL, 04al: InxnwJlateand remote prognostic slgnlfkance of fasolcular block dwlng acute myocardlal Infarctlon. Clrculatlon 47:765-775, 1973 5. Watua W, Mlzgefa HPzLong&m fxqoals of patients with lncompleta bilateral bundle branch block compllcatlng acute myocardlal Infarctlon: role of cardiac pacing. Am J Card10134:1-6.1974 6. Atktm JM, Lwhin &I, Blomqvlol CQ, et al: Ventricular conductlon blacks and sudden death In acute myocardlal Infarction: potential lndlcatlons for pacing. N Engl J Med 205:291-204, 1973 7. Rltlr WS, AtkIm JY, BlomqvM CQ, @Ilk Permanent pacing In patients wlth translent trlfascloutar block dwlng acute myocardlal Infarction. Am J Cardlol 39:205-209. 1976
References 1. 8Ohl a8, Flowlro MC. Hand RC, ot al: Superlwity of body surface map over electrocardloqam and vectorcardl~am In detecting abnormalltles in patients with severe coronary artery disease (abstr). Am J Cardiol 39:318. 1977
SPECIFICITY AND SENSITIVITY OF TECHNETIUM-QQM PYROPHOSPHATE MYOCARDIAL IMAGING IN ACUTE MYOCARDIAL INFARCTION
Berman et al.’ claim enhanced specificity of technetium-99m pyrophosphate myocardial imaging in acute myocardial in-
February 1976
The American Journalof CARDIOLOGY Volume 41
349
LETTERS TO THE EDITOR
farction by classifying as equivocal all scintigrams with a 2+ diffuse pattern. Their findings are of interest to us in view of our own data.2,3 Although a great majority of “false positive” technetium99m pyrophosphate scintigrams may show a 2+ diffuse pattern, we have found higher levels of diffuse uptake in patients without clinical evidence of acute myocardial infarctions with scintigrams obtained on more than one occasion 2 hours after pyrophosphate injection. With their new classification, Berman et al. were able to enhance the specificity of the technetium-99m pyrophosphate technique by excluding 35 patients without evidence of acute myocardial infarction on the basis of a 2+ diffuse or equivocal pattern. However, 9 of their 18 patients (50 percent) with subendocardial infarction, 5 of 81 patients (6 percent) with transmural infarction and 1 patient with equivocal evidence of infarction had the same 2+ diffuse or equivocal scintigraphic pattern. Thus only enzymatic and electrocardiographic changes separated the patients with myocardial infarction from those without such necrosis. The significance of a 2+ diffuse pattern in patients with coronary artery disease without enzymatic or electrocardiographic changes of acute myocardial infarction cannot be assessed without histologic data and long-term follow-up studies. Although residual cardiac blood pool activity may explain some of these equivocal scintigrams, it is not clear how, in the absence of histopathologic data, one can exclude subclinical myocardial necrosis as a possible mechanism of the 2+ diffuse pattern. By introducing the new equivocal category of positive technetium-99m pyrophosphate myocardial scintigrams, Berman et al. have tried to show increased specificity of this technique without giving the impression that its sensitivity is impaired. Whether the 2+ scintigram is classified as definitely positive or equivocal as Berman et al. suggest, one can improve upon the specificity of technetium-99m pyrophosphate imaging only at the cost of sensitivity and vice versa. Masood Ahmad, MD Veterans Administration Noninvasive Laboratory Department of Medicine Division of Cardiology University of Missouri Columbia School of Medicine C-7 Medical Center Columbia, Missouri
ization studies with left ventriculography and coronary arteriography revealed no cardiac disease, were without necrosis and had residual cardiac blood pool activity accounting for their 2+ diffuse pattern. Therefore, the specificity of the positive scintigram for acute infarction is increased by the categorization. In addition, by separating the equivocal group from patients with definitely negative scintigrams, the implication of the definitely negative study regarding absence of acute infarction is enhanced. Ahmad’s comments fail to consider the improved accuracy of both the positive and negative categories achieved by our new classification system, its major contribution. Necessarily, this markedly improved accuracy in definitely positive and definitely negative scintigraphy was achieved with modest loss of sensitivity. Thus, although most patients with 2+ diffuse uptake do not have necrosis, we do not not contend that all patients with such a pattern are never without myocardial necrosis. Indeed, when the 2+ pattern is seen, it is not possible to ascertain whether myocardial necrosis is or is not present. In this setting, the clinician must rely on the other standard methods for detecting myocardial necrosis. Importantly, myocardial technetium-99m scintigraphy may be performed serially or by computerized selective blood pool subtraction (Am J Cardiol, in press) to differentiate patients with 2+ diffuse activity due to acute necrosis from those with another cause of this pattern. Finally, no test in clinical medicine has absolute sensitivity and specificity. Indeed, the electrocardiogram, undoubtedly over time the single most useful tool for detection of infarction, frequently demonstrates nonspecific ST-T wave abnormalities. When these abnormalities are present, the electrocardiographer cannot state with confidence whether subendocardial ischemia or necrosis is present or absent. But the electrocardiogram may have Q waves with high diagnostic specificity for acute infarction. Only the staunchest of cynics would state that because electrocardiography frequently reveals nonspecific ST-T wave changes, it is not useful in the assessment of acute myocardial infarction. Technetium-99m pyrophosphate scintigraphy is not a perfect test for the diagnosis of infarction. However, if one is aware of the meaning of certain nonspecific patterns, the implications of the definitely positive and definitely negative pyrophosphate scintigram make the study considerably more useful in the clinical detection of acute myocardial infarction. Daniel S. Berman, MD, FACC Dean T. Mason, MD, FACC Cardiovascular Medicine University of California Davis, California
References 1. Berman SD, Amsterdam EA, Hlner HH, et al: New approach to interpretation Of technetium-99m pyrophosphate scintigraphy in detection of acute myocardial infarction. Am J Cardiol 39:341-346. 1977 2. Ahmad M. Dubiel JP, Verdee TA, et al: Technetium-99m stennous pyrophosphete myocerdiil imaging in patiente with and without left ventricular aneurysm. Circulation 53:633-630.1976 3. Ahmad M. Dublel JP, Verdon TA, et al: Limited clinical diagnostic specificity of technetiwn99m stannous pyrophosphate myocardial imaging in acute myocardial infarction. Am J Cardiol 3950-54. 1977
REPLY
Our new classification system is designed to maximize specificity while only minimally decreasing sensitivity. By using an equivocal category for the 2+ diffuse scintigram, we were able to exclude from the positive category many patients without myocardial necrosis by enzymatic or electrocardiographic criteria. Although a few of these patients may have had islands of subclinical myocardial necrosis, undoubtedly the great majority, especially those whose cardiac catheter-
350
February 1978
The American Journal of CARDIOLOGY
ABNORMAL P WAVE PATTERN IN REYE’S SYNDROME
Abnormal P wave patterns have been reported to occur as an electrocardiographic manifestation of focal disease of the central nervous system.1-3 Our recent experience with a 12 year old patient with Reye’s syndrome suggests (1) that such electrocardiographic findings may result from a nonfocal process in the central nervous system, and (2) that previous explanations for the electrocardiographic changes seen in Reye’s syndrome deserve to be reevaluated. Case summary: A 12 year old white girl was admitted to D.C. Children’s Hospital because of the gradual onset over 18 to 24 hours of delirium associated with nausea and vomiting. Upon admission, she was noted to be grossly disoriented.
Volume 41
VECTORCARDIOGRAPHY AND BODY SURFACE ISOPOTENTlAL MAPPING TO DETECT OLD MYOCARDIAL INFARCTION
TABLE I (Atkins et al.) One Year Follow-Up of Patients Who Had Third Degree A-V Block With Complete Right Bundle Branch Block Plus Left Anterior Hemiblock During Acute Myocardial Infarction Unpaced (no.) Ref
Patients
Deaths
3
:
5
z
2
06
6,7 21 Amikam and Riss Total
6
:
Paced (no.) Patients 0 7
1’2 2
I;:
0 41
: 21f51%)
: 26
Deaths :
0 2 8 1 3(12%)
A-V = atrioventricular; Ref = reference number.
Because our study was retrospective and unrandomized, the conclusion is not as strong scientifically as we and others would like. However, our statement that further randomized studies of patients in the group seem unjustified was based not only on the clear-cut difference in long-term prognosis in our series but also took into account the difficulties of attempting to assemble a randomized series. A case load of 500 acute myocardial infarctions per year would be likely to produce 25 patients with right bundle branch block plus left anterior hemiblock. Eleven of these 25 patients would manifest transient third degree A-V block and, of the 11 with such block, 5 would die in the hospital of pump failure, leaving 6 patients per year for randomization. Hence, to randomize enough patients to have 30 in each group would require 10 years. We believed it unjustified to initiate a study to randomize when the odds of obtaining scientifically valid information in a reasonable period of timeare nil and the principal reason for restraint is the expense of a pacemaker. A large multicenter trial to randomize patients may be justified because data on a substantial number of patients could be obtained in a reasonable amount of time and resolve this important problem. James M. Atkins, MD, FACC C. Gunnar Blomqvist, MD, FACC Charles 8. Mullins, MD, FACC Department of Internal Medicine The University of Texas Health Science Center Dallas, Texas
I enjoyed immensely the report by Vincent et al.’ on the contribution of body surface isopotential mapping to the diagnosis of old inferior myocardial infarction. Techniques useful in this diagnosis are of great practical import because QS or QR acute patterns of inferior leads in the standard electrocardiogram are often replaced by nondiagnostic qR or rS patterns. Vectorcardiography has also been found useful in detecting old inferior myocardial infarction in the absence of diagnostic Q waves in the inferior leads of the standard electrocardiogram. In addition, even inferior infarcts producing early inferiorly oriented forces and resulting in rS patterns in leads III and aVF have not escaped diagnosis by vectorcardiography. If the authors have recorded vectorcardiograms in their patients, I would be interested in the characteristics of the QRS loops of the frontal plane, particularly in their patients exemplified by Figures 5 and 6, who did not display diagnostic features of inferior myocardial infarction in the 12 lead electrocardiogram. John E. Madias, MD Cardiology Division Boston City Hospital Boston, Massachusetts References 1. Vlnconl GM. Ablldrkov JA, Burgen MJ, at ak Diagnosis of old inferior myocardial infarctlon bv bodv surface isowtential man&w. Am J Cardlol 39:510-515. 1977 2. LovIne H6, Vo&g E, Wlllla~r RA: Ele&&rdlogram and vectorcardiogram in myocardiil infarction. Circulation 45:457-470. 1972
REPLY
Although we recorded vectorcardiograms in some of our patients, the sampling is incomplete and the information not suitable for formal analysis. Vectorcardiography certainly seems to be superior to scalar electrocardiography in the diagnosis of previous inferior wall infarction. Sohi et al.’ have reported that the body surface map is superior to the scalar electrocardiogram and vectorcardiogram in detecting patients with previous infarction or severe coronary artery disease. Further comparison of body surface map data with vectorcardiographic data is necessary to establish the role of each of these procedures in the diagnosis of previous infarction. G. Michael Vincent, MD, FACC Department of Internal Medicine Alds Hospital Salt Lake City, Utah
References 1. ah*8 WR, Sutton R, Oh W, et al: Long-term prognosls after acute anterior infarction with atrloventrlcular block. Sr Marl J 39:198-199.1977 2. NlmotrAA,Shwoolu 85 Jr, Hullor AM Jr, et ak Slgnlfkxnce of bundle branch block during acute myocardtal lnfarctlon. Am Heart J 90~439-444, 1975 3. ScanIon PJ, Pryor R, I)lounl SQ h: Right bundle-branch block associated with left sup&or or Inferior lntraventrlcular block: associated with acute myocardlal InfarctIon. Clrculatlon 42:1135-1142. 1970 4. Wau# RA, Wm 08, Hw TL, 04al: InxnwJlateand remote prognostic slgnlfkance of fasolcular block dwlng acute myocardlal Infarctlon. Clrculatlon 47:765-775, 1973 5. Watua W, Mlzgefa HPzLong&m fxqoals of patients with lncompleta bilateral bundle branch block compllcatlng acute myocardlal Infarctlon: role of cardiac pacing. Am J Card10134:1-6.1974 6. Atktm JM, Lwhin &I, Blomqvlol CQ, et al: Ventricular conductlon blacks and sudden death In acute myocardlal Infarction: potential lndlcatlons for pacing. N Engl J Med 205:291-204, 1973 7. Rltlr WS, AtkIm JY, BlomqvM CQ, @Ilk Permanent pacing In patients wlth translent trlfascloutar block dwlng acute myocardlal Infarction. Am J Cardlol 39:205-209. 1976
References 1. 8Ohl a8, Flowlro MC. Hand RC, ot al: Superlwity of body surface map over electrocardloqam and vectorcardl~am In detecting abnormalltles in patients with severe coronary artery disease (abstr). Am J Cardiol 39:318. 1977
SPECIFICITY AND SENSITIVITY OF TECHNETIUM-QQM PYROPHOSPHATE MYOCARDIAL IMAGING IN ACUTE MYOCARDIAL INFARCTION
Berman et al.’ claim enhanced specificity of technetium-99m pyrophosphate myocardial imaging in acute myocardial in-
February 1976
The American Journalof CARDIOLOGY Volume 41
349
LETTERS TO THE EDITOR
farction by classifying as equivocal all scintigrams with a 2+ diffuse pattern. Their findings are of interest to us in view of our own data.2,3 Although a great majority of “false positive” technetium99m pyrophosphate scintigrams may show a 2+ diffuse pattern, we have found higher levels of diffuse uptake in patients without clinical evidence of acute myocardial infarctions with scintigrams obtained on more than one occasion 2 hours after pyrophosphate injection. With their new classification, Berman et al. were able to enhance the specificity of the technetium-99m pyrophosphate technique by excluding 35 patients without evidence of acute myocardial infarction on the basis of a 2+ diffuse or equivocal pattern. However, 9 of their 18 patients (50 percent) with subendocardial infarction, 5 of 81 patients (6 percent) with transmural infarction and 1 patient with equivocal evidence of infarction had the same 2+ diffuse or equivocal scintigraphic pattern. Thus only enzymatic and electrocardiographic changes separated the patients with myocardial infarction from those without such necrosis. The significance of a 2+ diffuse pattern in patients with coronary artery disease without enzymatic or electrocardiographic changes of acute myocardial infarction cannot be assessed without histologic data and long-term follow-up studies. Although residual cardiac blood pool activity may explain some of these equivocal scintigrams, it is not clear how, in the absence of histopathologic data, one can exclude subclinical myocardial necrosis as a possible mechanism of the 2+ diffuse pattern. By introducing the new equivocal category of positive technetium-99m pyrophosphate myocardial scintigrams, Berman et al. have tried to show increased specificity of this technique without giving the impression that its sensitivity is impaired. Whether the 2+ scintigram is classified as definitely positive or equivocal as Berman et al. suggest, one can improve upon the specificity of technetium-99m pyrophosphate imaging only at the cost of sensitivity and vice versa. Masood Ahmad, MD Veterans Administration Noninvasive Laboratory Department of Medicine Division of Cardiology University of Missouri Columbia School of Medicine C-7 Medical Center Columbia, Missouri
ization studies with left ventriculography and coronary arteriography revealed no cardiac disease, were without necrosis and had residual cardiac blood pool activity accounting for their 2+ diffuse pattern. Therefore, the specificity of the positive scintigram for acute infarction is increased by the categorization. In addition, by separating the equivocal group from patients with definitely negative scintigrams, the implication of the definitely negative study regarding absence of acute infarction is enhanced. Ahmad’s comments fail to consider the improved accuracy of both the positive and negative categories achieved by our new classification system, its major contribution. Necessarily, this markedly improved accuracy in definitely positive and definitely negative scintigraphy was achieved with modest loss of sensitivity. Thus, although most patients with 2+ diffuse uptake do not have necrosis, we do not not contend that all patients with such a pattern are never without myocardial necrosis. Indeed, when the 2+ pattern is seen, it is not possible to ascertain whether myocardial necrosis is or is not present. In this setting, the clinician must rely on the other standard methods for detecting myocardial necrosis. Importantly, myocardial technetium-99m scintigraphy may be performed serially or by computerized selective blood pool subtraction (Am J Cardiol, in press) to differentiate patients with 2+ diffuse activity due to acute necrosis from those with another cause of this pattern. Finally, no test in clinical medicine has absolute sensitivity and specificity. Indeed, the electrocardiogram, undoubtedly over time the single most useful tool for detection of infarction, frequently demonstrates nonspecific ST-T wave abnormalities. When these abnormalities are present, the electrocardiographer cannot state with confidence whether subendocardial ischemia or necrosis is present or absent. But the electrocardiogram may have Q waves with high diagnostic specificity for acute infarction. Only the staunchest of cynics would state that because electrocardiography frequently reveals nonspecific ST-T wave changes, it is not useful in the assessment of acute myocardial infarction. Technetium-99m pyrophosphate scintigraphy is not a perfect test for the diagnosis of infarction. However, if one is aware of the meaning of certain nonspecific patterns, the implications of the definitely positive and definitely negative pyrophosphate scintigram make the study considerably more useful in the clinical detection of acute myocardial infarction. Daniel S. Berman, MD, FACC Dean T. Mason, MD, FACC Cardiovascular Medicine University of California Davis, California
References 1. Berman SD, Amsterdam EA, Hlner HH, et al: New approach to interpretation Of technetium-99m pyrophosphate scintigraphy in detection of acute myocardial infarction. Am J Cardiol 39:341-346. 1977 2. Ahmad M. Dubiel JP, Verdee TA, et al: Technetium-99m stennous pyrophosphete myocerdiil imaging in patiente with and without left ventricular aneurysm. Circulation 53:633-630.1976 3. Ahmad M. Dublel JP, Verdon TA, et al: Limited clinical diagnostic specificity of technetiwn99m stannous pyrophosphate myocardial imaging in acute myocardial infarction. Am J Cardiol 3950-54. 1977
REPLY
Our new classification system is designed to maximize specificity while only minimally decreasing sensitivity. By using an equivocal category for the 2+ diffuse scintigram, we were able to exclude from the positive category many patients without myocardial necrosis by enzymatic or electrocardiographic criteria. Although a few of these patients may have had islands of subclinical myocardial necrosis, undoubtedly the great majority, especially those whose cardiac catheter-
350
February 1978
The American Journal of CARDIOLOGY
ABNORMAL P WAVE PATTERN IN REYE’S SYNDROME
Abnormal P wave patterns have been reported to occur as an electrocardiographic manifestation of focal disease of the central nervous system.1-3 Our recent experience with a 12 year old patient with Reye’s syndrome suggests (1) that such electrocardiographic findings may result from a nonfocal process in the central nervous system, and (2) that previous explanations for the electrocardiographic changes seen in Reye’s syndrome deserve to be reevaluated. Case summary: A 12 year old white girl was admitted to D.C. Children’s Hospital because of the gradual onset over 18 to 24 hours of delirium associated with nausea and vomiting. Upon admission, she was noted to be grossly disoriented.
Volume 41
