rhythmia. The patient was discharged from the hospital on Feb 20 , 1975 in good condition. A follow-up in July 1975 confirme d thi s result. DISCUSSION
This typ e of cardiac malrotation has been called mixed dextrocardia with ventricular inversion,' and dextrocardia with situs solitus and l-transposition.2 Corrected transposition of th e grea t vesse ls associat ed with cardiac dextrorotation" was the most frequent typ e of dextrocardia, occurring in 29 percent ( 15) of 51 autopsied cases.' Frequently, in patients with inv ersion of th e ventricles, th e great vessels ar e also inv erted and, in addition, tr ansposed . I insist that in corrected transposition of the great vessels with cardiac dextrorotation, repl acem ent of the left atrioventricul ar valv e can b e performed easily from a technical standpoint. On th e contra ry, in corrected tr ansposition associated with mirror-image dextrocardia ( synonyms, mixed dextro cardia with atrial inv ersion ; dextrocardia with situs inversus and d-transposition ), exposure of th e left atrioventricular area ma y be rather difficult."
FIGURE 1. Medi al and supe rficial position of left atrium ( LA) perm its exce llent expos ure of left atr ioventric ular valve. LV , Arte rial ventricle, anatomic right ventr icle; RV, ven ous ventricle, anatomic left ventricle; RA, right atrium ; Ao, aorta; CxA, circumflex art ery ; and ADCA, anterior descending coronary artery . ( v wave, 70 mm Hg , and y wave, 20 mm Hg ). Oximetric data dem onst rat ed absence of left-t o-ri ght shunt. Angtocardi ographic stu d ies showed that th e right atrium and sup erior and inferior venae cavae we re in th eir normal positions and to th e right of the left atrium (s itus solitus) . Th e venous ventricle was situa te d on the right side and posterocephalad to th e arte ria l ven tricle. Th e art eri al ventriculogram demonstrated the p resen ce of tra beculae and a crista sup rave ntricularis compa tible with an anatomic right ventr icle . Th e systolic and di ast olic volum es we re greatly augm ented . Th e aorta aro se from th e art eri al ventr icle and lay to th e left and anteri or of the ma in pulmonar y artery. The convexity of the ascending ao rta lay to the left of th e spinal column. Th e aort ic valve was situated ceph alad to th e pulmonary arte rial valve and without continuity with th e left atri oventri cular valve. Surgery was performed on Feb 1, 1975. The heart was app roache d through a .med ian ste rno tomy . Th e exte rn al diameter s of the ascending aorta and main pulmonary ar tery were 25 and 65 mm , respect ively. Th e righ t atr ium, th e venous ventricle, and the inferior ven a cava were situ ate d posterior to th e arte rial ventricle . Cannulati on of th e superior vena cava was performed th rou gh th e right atrial appe ndage, and the inferior vena cava was can nulated via th e left femoral vein. Th e left-sided atr ioventricular valv e was tri cuspid; it was eas ily replaced th rou gh th e dil ated and sup er ficial left atrium with a No. 29 Bjork p rosth esis ( Fig 1 ). Du ring the ea rly postoperative peri od, th e patient required digitali s for the treatment of card iac failure and tach yar -
246 COMMUNICATIONS TO THE EDITOR
Domingo Liotta, M.D. , F.C.C.P. Hospital Italiano Bu eno s Aires REFERENCES
1 Arcilla RA, Gesul BM : Con genital dextrocard ia : Clinical , ang iograp hic and autops y studies on 50 patients. J Ped iatr 58:39, 1961 2 Van Pra agh R, Van Pr aagh S, Vlad P, et al : Diagnosis of th e anat om ic typ es of congenita l dextr ocardia. Am J CardioI15 :234, 1965 3 De la Cruz MV, Polansky BJ, Navarro Lopez F : Th e diagno sis of correc te d transposition of th e great vessels. Br Hea rt J 24: 483, 1962 4 Van Pr aagh R, Van Praagh S, Vlad P, et al: Anatomic types of congenital dextrocardia : Diagnostic and embryologic impli cati ons. Am J Cardiel 13:510, 1964 5 Liotta D, Ferrari HM , Pisanu A, et al: Sur gical treatment of left at rioventricular valve insufficiency in conge nita l dextrocardi a. Prensa Med Argentina 62 :177-181 , 1975
Blood Gas Analysis during Hemodialysis T o th e Editor: W e read with int erest the article entitled "Evi dence for Pulmonary Microembolization during Hemodialysis" by Bisch el et al in th e March issue ( C hest 67 :335-337, 1975 ); how ever, we' have published data whi ch ar e at va riance with th eir findin gs and int erpretation. Mea surem ent of respiratory gas excha nge , as well as blood gas levels , reveals that
CHEST, 69: 2, FEBRUARY, 1976
due to an increase in oxygen consumption (V0 2) and a decrease in carbon dioxide production (VC02), the respiratory quotient (VC02/V02) falls from a normal mean of 0.82 to about 0.65. These changes occur early during hemodialysis and persist at least one hour after dialysis. When alveolar oxygen pressure is calculated from the measured VC02/ Vo2, it decreases; arterial oxygen pressure (Pa02) decreases, and no significant change in the alveolararterial oxygen pressure difference occurs. Our data are consistent with decreased alveolar ventilation and do not support a ventilation-perfusion abnormality which one would expect with microembolization. Bischel and associates, however, do find that the use of filters prevents the significant fall in Pa02 measured after dialysis. The reason for this is unclear and might be best approached by simultaneous measurement of both blood and respiratory gas levels. Joseph M. Letteri, M.D. Joel E. Sherlock, M.D. and James W. Ledwith, M.D., F.C.C.P. Renal and Pulmonary Divisions Nassau County Medical Center State University of New York at Stony Brook REFERENCE
1 Sherlock IE, Yoon Y, Ledwith JW, et al: Respiratory gas exchange during hemodialysis. In Proceedings of the Clinical Dialysis and Transplant Forum (vol 2) ( Schreiner GE, ed). Washington, DC, Georgetown University Press, 1972, pp 171-174
To the Editor: Drs. Letteri, Sherlock, and Ledwith have commented on their observed changes in the alveolar oxygen pressure consequent to changes in the respiratory quotient. Our study was not designed to answer this question; and, indeed, it is most proper to measure the respiratory quotient if one were to point out changes in the alveolar-arterial oxygen pressure difference before, during, or after dialysis. Our study was designed to answer questions on the effect of a filter vs no filter. Our assumption of the respiratory quotient is then a systematic error which is effectively cancelled out by paired analysis. We also note that the article by Sherlock et al' describes the use of a specific commercial model of blood gas analyzer (Instrumentation Laboratories model 313). The function of various commercially available blood gas analyzers has been studied." the results are shown in Table 1. We have repeatedly demonstrated that the speCHEST, 69: 2, FEBRUARY, 1976
Table I-Analysis o] PaO z Data Derived by Various Blood Gas Analyzers Analyzer Radiometer Model BMS-3
Ll.x
a
n
0.7
5.1
260
1.1 1.1
28 74 26 114
Instrumentation Laboratories Model Model Model Corning Model
113 213 313
11.5
4.7 3.7 5.6
165
4.6
4.5
cific model of blood gas analyzer used by Sherlock et al' exceeds the estimate of arterial oxygen pressure (Pa02) by an average of 11.5 mm Hg. Since this specific model of blood gas analyzer was used by these investigators, it is fair to assume that the data for Pa02 reported by Letteri et al are also similarly in excess. Taking this fact into account, correction of their data would then agree with ours. Margaret D. Bischel, M.D. Lutheran General Hospital, Park Ridge, III and John G. Mohler, M.D. Los Angeles County-University of Southern California Medical Center, Los Angeles REFERENCES
1 Sherlock JE, Yoon Y, Ledwith JW, et al: Respiratory gas exchange during hemodialysis. In Proceedings of the Clinical Dialysis and Transplant Forum (vol 2) (S.::hreiner GE, ed ). Washington, DC, Georgetown University Press, 1972, pp 171-174 2 Mohler IG: Devices for blood gas analysis. N Engl J Med 290:632-633, 1974
Ventricular Fibrillation Induced by a Defective Demand Pacemaker To the Editor: Although the occurrence of pacemaker-induced tachycardia or so-called "runaway" pacemakers is a rare event due to the modern design of pacemakers, it still may occur and has been seen in some pacemakers manufactured around 1972. The case we report here is that of a patient who, upon admission to the hospital, presented with a pacemaker rate of 210 beats per minute, which increased to 2,000 beats per minute within five minutes, followed by loss of capture and ventricular fibrillation. CASE REPORT
A 44-year-old man with congenital heart block had a unipolar pacemaker implanted in February 1973 in another hospital. A few months after implantation, the patient devel-
COMMUNICATIONS TO THE EDITOR 247
This typ e of cardiac malrotation has been called mixed dextrocardia with ventricular inversion,' and dextrocardia with situs solitus and l-transposition.2 Corrected transposition of th e grea t vesse ls associat ed with cardiac dextrorotation" was the most frequent typ e of dextrocardia, occurring in 29 percent ( 15) of 51 autopsied cases.' Frequently, in patients with inv ersion of th e ventricles, th e great vessels ar e also inv erted and, in addition, tr ansposed . I insist that in corrected transposition of the great vessels with cardiac dextrorotation, repl acem ent of the left atrioventricul ar valv e can b e performed easily from a technical standpoint. On th e contra ry, in corrected tr ansposition associated with mirror-image dextrocardia ( synonyms, mixed dextro cardia with atrial inv ersion ; dextrocardia with situs inversus and d-transposition ), exposure of th e left atrioventricular area ma y be rather difficult."
FIGURE 1. Medi al and supe rficial position of left atrium ( LA) perm its exce llent expos ure of left atr ioventric ular valve. LV , Arte rial ventricle, anatomic right ventr icle; RV, ven ous ventricle, anatomic left ventricle; RA, right atrium ; Ao, aorta; CxA, circumflex art ery ; and ADCA, anterior descending coronary artery . ( v wave, 70 mm Hg , and y wave, 20 mm Hg ). Oximetric data dem onst rat ed absence of left-t o-ri ght shunt. Angtocardi ographic stu d ies showed that th e right atrium and sup erior and inferior venae cavae we re in th eir normal positions and to th e right of the left atrium (s itus solitus) . Th e venous ventricle was situa te d on the right side and posterocephalad to th e arte ria l ven tricle. Th e art eri al ventriculogram demonstrated the p resen ce of tra beculae and a crista sup rave ntricularis compa tible with an anatomic right ventr icle . Th e systolic and di ast olic volum es we re greatly augm ented . Th e aorta aro se from th e art eri al ventr icle and lay to th e left and anteri or of the ma in pulmonar y artery. The convexity of the ascending ao rta lay to the left of th e spinal column. Th e aort ic valve was situated ceph alad to th e pulmonary arte rial valve and without continuity with th e left atri oventri cular valve. Surgery was performed on Feb 1, 1975. The heart was app roache d through a .med ian ste rno tomy . Th e exte rn al diameter s of the ascending aorta and main pulmonary ar tery were 25 and 65 mm , respect ively. Th e righ t atr ium, th e venous ventricle, and the inferior ven a cava were situ ate d posterior to th e arte rial ventricle . Cannulati on of th e superior vena cava was performed th rou gh th e right atrial appe ndage, and the inferior vena cava was can nulated via th e left femoral vein. Th e left-sided atr ioventricular valv e was tri cuspid; it was eas ily replaced th rou gh th e dil ated and sup er ficial left atrium with a No. 29 Bjork p rosth esis ( Fig 1 ). Du ring the ea rly postoperative peri od, th e patient required digitali s for the treatment of card iac failure and tach yar -
246 COMMUNICATIONS TO THE EDITOR
Domingo Liotta, M.D. , F.C.C.P. Hospital Italiano Bu eno s Aires REFERENCES
1 Arcilla RA, Gesul BM : Con genital dextrocard ia : Clinical , ang iograp hic and autops y studies on 50 patients. J Ped iatr 58:39, 1961 2 Van Pra agh R, Van Pr aagh S, Vlad P, et al : Diagnosis of th e anat om ic typ es of congenita l dextr ocardia. Am J CardioI15 :234, 1965 3 De la Cruz MV, Polansky BJ, Navarro Lopez F : Th e diagno sis of correc te d transposition of th e great vessels. Br Hea rt J 24: 483, 1962 4 Van Pr aagh R, Van Praagh S, Vlad P, et al: Anatomic types of congenital dextrocardia : Diagnostic and embryologic impli cati ons. Am J Cardiel 13:510, 1964 5 Liotta D, Ferrari HM , Pisanu A, et al: Sur gical treatment of left at rioventricular valve insufficiency in conge nita l dextrocardi a. Prensa Med Argentina 62 :177-181 , 1975
Blood Gas Analysis during Hemodialysis T o th e Editor: W e read with int erest the article entitled "Evi dence for Pulmonary Microembolization during Hemodialysis" by Bisch el et al in th e March issue ( C hest 67 :335-337, 1975 ); how ever, we' have published data whi ch ar e at va riance with th eir findin gs and int erpretation. Mea surem ent of respiratory gas excha nge , as well as blood gas levels , reveals that
CHEST, 69: 2, FEBRUARY, 1976
due to an increase in oxygen consumption (V0 2) and a decrease in carbon dioxide production (VC02), the respiratory quotient (VC02/V02) falls from a normal mean of 0.82 to about 0.65. These changes occur early during hemodialysis and persist at least one hour after dialysis. When alveolar oxygen pressure is calculated from the measured VC02/ Vo2, it decreases; arterial oxygen pressure (Pa02) decreases, and no significant change in the alveolararterial oxygen pressure difference occurs. Our data are consistent with decreased alveolar ventilation and do not support a ventilation-perfusion abnormality which one would expect with microembolization. Bischel and associates, however, do find that the use of filters prevents the significant fall in Pa02 measured after dialysis. The reason for this is unclear and might be best approached by simultaneous measurement of both blood and respiratory gas levels. Joseph M. Letteri, M.D. Joel E. Sherlock, M.D. and James W. Ledwith, M.D., F.C.C.P. Renal and Pulmonary Divisions Nassau County Medical Center State University of New York at Stony Brook REFERENCE
1 Sherlock IE, Yoon Y, Ledwith JW, et al: Respiratory gas exchange during hemodialysis. In Proceedings of the Clinical Dialysis and Transplant Forum (vol 2) ( Schreiner GE, ed). Washington, DC, Georgetown University Press, 1972, pp 171-174
To the Editor: Drs. Letteri, Sherlock, and Ledwith have commented on their observed changes in the alveolar oxygen pressure consequent to changes in the respiratory quotient. Our study was not designed to answer this question; and, indeed, it is most proper to measure the respiratory quotient if one were to point out changes in the alveolar-arterial oxygen pressure difference before, during, or after dialysis. Our study was designed to answer questions on the effect of a filter vs no filter. Our assumption of the respiratory quotient is then a systematic error which is effectively cancelled out by paired analysis. We also note that the article by Sherlock et al' describes the use of a specific commercial model of blood gas analyzer (Instrumentation Laboratories model 313). The function of various commercially available blood gas analyzers has been studied." the results are shown in Table 1. We have repeatedly demonstrated that the speCHEST, 69: 2, FEBRUARY, 1976
Table I-Analysis o] PaO z Data Derived by Various Blood Gas Analyzers Analyzer Radiometer Model BMS-3
Ll.x
a
n
0.7
5.1
260
1.1 1.1
28 74 26 114
Instrumentation Laboratories Model Model Model Corning Model
113 213 313
11.5
4.7 3.7 5.6
165
4.6
4.5
cific model of blood gas analyzer used by Sherlock et al' exceeds the estimate of arterial oxygen pressure (Pa02) by an average of 11.5 mm Hg. Since this specific model of blood gas analyzer was used by these investigators, it is fair to assume that the data for Pa02 reported by Letteri et al are also similarly in excess. Taking this fact into account, correction of their data would then agree with ours. Margaret D. Bischel, M.D. Lutheran General Hospital, Park Ridge, III and John G. Mohler, M.D. Los Angeles County-University of Southern California Medical Center, Los Angeles REFERENCES
1 Sherlock JE, Yoon Y, Ledwith JW, et al: Respiratory gas exchange during hemodialysis. In Proceedings of the Clinical Dialysis and Transplant Forum (vol 2) (S.::hreiner GE, ed ). Washington, DC, Georgetown University Press, 1972, pp 171-174 2 Mohler IG: Devices for blood gas analysis. N Engl J Med 290:632-633, 1974
Ventricular Fibrillation Induced by a Defective Demand Pacemaker To the Editor: Although the occurrence of pacemaker-induced tachycardia or so-called "runaway" pacemakers is a rare event due to the modern design of pacemakers, it still may occur and has been seen in some pacemakers manufactured around 1972. The case we report here is that of a patient who, upon admission to the hospital, presented with a pacemaker rate of 210 beats per minute, which increased to 2,000 beats per minute within five minutes, followed by loss of capture and ventricular fibrillation. CASE REPORT
A 44-year-old man with congenital heart block had a unipolar pacemaker implanted in February 1973 in another hospital. A few months after implantation, the patient devel-
COMMUNICATIONS TO THE EDITOR 247
