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Stress testing after successful percutaneous transluminal coronary angioplasty
LETTERS*
OPTIMAL TRANSESOPNACEAL ATRIA1 PACING Nishimura et al* described their experience trying to delineate the optimal method of transesophageal atria1 pacing. Their study containsseveral potential faults anddiscrepancies. The principal discrepancy from ofher published work is the extremely high pacing thresholds achieved. The lowest threshold of 27 i 7 mA was found at a pulse width of 8 ms and an interpolar distance of 24 mm. Thisvalue is markedly higher than that in other other studies. Gallagher et al2 reported thresholds using an int,erpolar distance of 29 mm and pulse durations of 0.5 to 9.9 ms. The minimal thresholdwasll %SmAatapulsedurationof 9.9ms, lessthan 50% ofthevaluefoundin this study. In our experience of studying approximately 150 patients by this technique, we have rarely required a current of more fhan 15 mA to sustain adequate capture, even for rapid burst pacing to terminate atria1 flutter or supraventricular tachycardia. This discrepancy has 2 possible explanations. The first is the catheter used. The hexipolar catheter has a surface area of 12 mmz, which is similar to the proximal pole of the Medtronic6992electrodeusedinGallagher’s work. Consequently this does not appear to be a maj or difference. The catheter itself may be different in that the hexipolar catheter appears to be a stiff catheter that maylie slightly differently in the esophagus and, in fact, because of the curve of its insertion through the mouth may displace the esophagus posteriorly. Another, more likely explanation is the stimulator used. The investigators point out that the stimulator (Nihon: Kohden, SEN7103) was shown to deliver a constant current in the presence of resistances of 0 to 1,000 Q. They do not discuss the voltage of the power source. Transesophageal atria1 pacing has an impedance of 1,000 to 2,000 a, and a stimulator with a power source of less than 40 V is required to deliver constant current against these types of resistances. The investigators do not appear to have actually measured the current that was delivered, and they may have delivered significantly less current than reported. This, therefore, leaves the results in question. My other criticism in terms of defining the optimal method of transesophageal pacing is the choice of catheters. The hexipolar catheter appearsstiff and isintroduced throughthe mouth. We have tried similar catheters and because of the stiffness have found that they create a significant amount of discomfort. We
* Letters (from the United States) concerning a particular article in the Journal must be received within 2 months of the article’s publication, and should be limited (with rare exceptions) to 2 double-spaced typewritten pages. Two copies must be submitted.
also have performed transesophageal pacing through the mouth with various leads and found that this causes considerably greater gagging than through the nose. We consequently use No. 9 or No. 4 soft polyurethane catheters, introduced transnasally, and patients experience minimal discomfort. Therefore, I thinkreadersshould be aware that the currents reported in this article may be excessive and may result in a burning of the esophagus. This is particularly important in patients presenting wifh supraventricular arrhythmias because atria1 capture is sometimes difficult to prove and arbitrary currents are used until arrhythmia termination is achieved. Although Nishimura et al pointed out interesting observations, they neglected some of the principles that are important in transesophageal atria1 pacing and neglected to rationalize discrepancies from previous observations. CHARLES R. KERR, MD Vancouver, Canada 2 June 1986 1. Nishimura
M, Katch T. Hanai S. Watanabe Y. OptimalmodeoftransesophogeoIotrioIpocing.Am J Cardiol 1986;57:791-796. 2. Gallagher JJ.Smith WM, Kerr CR, Kasell J, Cook L, Reiter M, Sterba R, Harte M. Esophageal pacing: a diagnostic and therapeutic tool. Circulation 1982; 65:336-341.
STRESS TESTING AFTER SUCCESSFUL PERCUTANEOUS TRANSLUMINAL CORONARY ANGIOPLASTY We were interested to read the experience of Nygaard et al,’ concerning the occurrence of acute coronary occlusion during exercise testing soon after successful percutaneous transluminal coronary angioplasty (PTCA) of the left anterior descending coronary artery. They state that “only 1 previous case of acute occlusion has been documented that temporally appears to be related to the exercise test” (referring to Dash2). Apparently, they are unaware of our report, “Acute Coronary Thrombus Formation After Stress Testing FollowingPercutaneousTransluminalCoronary Atigioplasty: A Case Report,“3 which was published on March 9.1985, and antedated their publication. Our experience was that of a 37-year-old man presentingwithunstable angina pectoris who underwent successful PTCA of a 95% right coronary artery stenosis. Submaximal treadmill stress testing 3 days after PTCA resulted in a hyperacute transmural inferior myocardial infarction within 30 minutes of commencing the stress test. Immediate coronary angiography revealedarecentthrombusrelatedtothePTCA site, which was successfully lysed with intracoronary streptokinase. We suggested that “testing to assess the efficacy of PTCA be de644
ferred until at least 1 month after the procedure to allow for completion of the healing process. ” In fact, we already made this suggestion in our review article on PTCA4 published on January 25,1984, in light of our experience, as well as of the research work of Mehta et a1,5who clearly showed that TXAz levels increased out of proportion to PGIzlevels in patients with documented coronary atherosclerosis during exercise stress testing, favoring the role of coronary artery spasm. We agree with Nygaard et all in their comments regarding the delaying of such a stress test to “2 weeks to 1 month” after PTCA, particularly in patients who have undergone a “complicated course.” JERZV 2. PRZVBOJEWSKI, MB, CHB, FCP (M) HELLMUTH F.H. WEIGH, MD Tygerberg, South Africa 5 June 1986 1. Nygaard
TW, Beller GA, Mentzer RM, Gibson RS, Moeller CM, Burwell LR. Acute coronary occlusion with exercise testing after initially successful coronary angioplasty for acute myocardial infarction. Am J CardioI1986;57:687-688. 2. Dash H. Delayed coronary occlusion after successful percutaneous tronsluminol coronary ongioplasty: association with exercise testing. Am J Cordial 1982;52:1143-1144. 3. Pryzbojewski JZ, Weich HFH. Acute coronary thrombus formation after stress testing following percutaneous tronsluminal coronary angioplasty: o case report. S Afr Med J 1985;67:378-382. 4. Przybojewski JZ, Weich HFH. Percutaneous tronsluminol coronary angioplasty: o review of the Iiteroture. S Afr Med J 1984;65:(Jonuory):l-22. 5. Mehta J, Mehta P, Horalek C. The significance of platelet-vessel wall prostaglandin equilibrium during exercise-induced stress. Am Heart J 1983;105: 895-900.
CORONARY ANGIOPLASTY BALLOON COMPLIANCE AND TEMPERATURE The article by Jain et al1 addressed an important aspect of coronary balloon catheter angioplasty: the effective diameter of the different balloons at progressive inflating pressures. These data are essential for an appropriate choice of the balloon catheter and of the inflating pressure, z major determinants of the degree of relief of the stenosis, of the incidence of initial dissection and, probably, oftherestenosisrate.Theirconclusionswere: the Advanced Cardiovascular System (ACS) balloons are smaller at equal pressure of inflation and they have similar compliance to the polyvinyl chloride (USCI) counterparts1 As the daily experience in clinical angioplasty suggests a substantially different behavior of the z types of catheters, I compared the above data to those available from the catheter message,
manufacturers.z*s To simplify the the USC1 data2 indicate a relative
change of their 2.5-mm balloon (LPS-I] diameter of 12% (from 2.25 to 2.73 mm) when he inflation pressure is increased from 4 to 10
OPTIMAL TRANSESOPNACEAL ATRIA1 PACING Nishimura et al* described their experience trying to delineate the optimal method of transesophageal atria1 pacing. Their study containsseveral potential faults anddiscrepancies. The principal discrepancy from ofher published work is the extremely high pacing thresholds achieved. The lowest threshold of 27 i 7 mA was found at a pulse width of 8 ms and an interpolar distance of 24 mm. Thisvalue is markedly higher than that in other other studies. Gallagher et al2 reported thresholds using an int,erpolar distance of 29 mm and pulse durations of 0.5 to 9.9 ms. The minimal thresholdwasll %SmAatapulsedurationof 9.9ms, lessthan 50% ofthevaluefoundin this study. In our experience of studying approximately 150 patients by this technique, we have rarely required a current of more fhan 15 mA to sustain adequate capture, even for rapid burst pacing to terminate atria1 flutter or supraventricular tachycardia. This discrepancy has 2 possible explanations. The first is the catheter used. The hexipolar catheter has a surface area of 12 mmz, which is similar to the proximal pole of the Medtronic6992electrodeusedinGallagher’s work. Consequently this does not appear to be a maj or difference. The catheter itself may be different in that the hexipolar catheter appears to be a stiff catheter that maylie slightly differently in the esophagus and, in fact, because of the curve of its insertion through the mouth may displace the esophagus posteriorly. Another, more likely explanation is the stimulator used. The investigators point out that the stimulator (Nihon: Kohden, SEN7103) was shown to deliver a constant current in the presence of resistances of 0 to 1,000 Q. They do not discuss the voltage of the power source. Transesophageal atria1 pacing has an impedance of 1,000 to 2,000 a, and a stimulator with a power source of less than 40 V is required to deliver constant current against these types of resistances. The investigators do not appear to have actually measured the current that was delivered, and they may have delivered significantly less current than reported. This, therefore, leaves the results in question. My other criticism in terms of defining the optimal method of transesophageal pacing is the choice of catheters. The hexipolar catheter appearsstiff and isintroduced throughthe mouth. We have tried similar catheters and because of the stiffness have found that they create a significant amount of discomfort. We
* Letters (from the United States) concerning a particular article in the Journal must be received within 2 months of the article’s publication, and should be limited (with rare exceptions) to 2 double-spaced typewritten pages. Two copies must be submitted.
also have performed transesophageal pacing through the mouth with various leads and found that this causes considerably greater gagging than through the nose. We consequently use No. 9 or No. 4 soft polyurethane catheters, introduced transnasally, and patients experience minimal discomfort. Therefore, I thinkreadersshould be aware that the currents reported in this article may be excessive and may result in a burning of the esophagus. This is particularly important in patients presenting wifh supraventricular arrhythmias because atria1 capture is sometimes difficult to prove and arbitrary currents are used until arrhythmia termination is achieved. Although Nishimura et al pointed out interesting observations, they neglected some of the principles that are important in transesophageal atria1 pacing and neglected to rationalize discrepancies from previous observations. CHARLES R. KERR, MD Vancouver, Canada 2 June 1986 1. Nishimura
M, Katch T. Hanai S. Watanabe Y. OptimalmodeoftransesophogeoIotrioIpocing.Am J Cardiol 1986;57:791-796. 2. Gallagher JJ.Smith WM, Kerr CR, Kasell J, Cook L, Reiter M, Sterba R, Harte M. Esophageal pacing: a diagnostic and therapeutic tool. Circulation 1982; 65:336-341.
STRESS TESTING AFTER SUCCESSFUL PERCUTANEOUS TRANSLUMINAL CORONARY ANGIOPLASTY We were interested to read the experience of Nygaard et al,’ concerning the occurrence of acute coronary occlusion during exercise testing soon after successful percutaneous transluminal coronary angioplasty (PTCA) of the left anterior descending coronary artery. They state that “only 1 previous case of acute occlusion has been documented that temporally appears to be related to the exercise test” (referring to Dash2). Apparently, they are unaware of our report, “Acute Coronary Thrombus Formation After Stress Testing FollowingPercutaneousTransluminalCoronary Atigioplasty: A Case Report,“3 which was published on March 9.1985, and antedated their publication. Our experience was that of a 37-year-old man presentingwithunstable angina pectoris who underwent successful PTCA of a 95% right coronary artery stenosis. Submaximal treadmill stress testing 3 days after PTCA resulted in a hyperacute transmural inferior myocardial infarction within 30 minutes of commencing the stress test. Immediate coronary angiography revealedarecentthrombusrelatedtothePTCA site, which was successfully lysed with intracoronary streptokinase. We suggested that “testing to assess the efficacy of PTCA be de644
ferred until at least 1 month after the procedure to allow for completion of the healing process. ” In fact, we already made this suggestion in our review article on PTCA4 published on January 25,1984, in light of our experience, as well as of the research work of Mehta et a1,5who clearly showed that TXAz levels increased out of proportion to PGIzlevels in patients with documented coronary atherosclerosis during exercise stress testing, favoring the role of coronary artery spasm. We agree with Nygaard et all in their comments regarding the delaying of such a stress test to “2 weeks to 1 month” after PTCA, particularly in patients who have undergone a “complicated course.” JERZV 2. PRZVBOJEWSKI, MB, CHB, FCP (M) HELLMUTH F.H. WEIGH, MD Tygerberg, South Africa 5 June 1986 1. Nygaard
TW, Beller GA, Mentzer RM, Gibson RS, Moeller CM, Burwell LR. Acute coronary occlusion with exercise testing after initially successful coronary angioplasty for acute myocardial infarction. Am J CardioI1986;57:687-688. 2. Dash H. Delayed coronary occlusion after successful percutaneous tronsluminol coronary ongioplasty: association with exercise testing. Am J Cordial 1982;52:1143-1144. 3. Pryzbojewski JZ, Weich HFH. Acute coronary thrombus formation after stress testing following percutaneous tronsluminal coronary angioplasty: o case report. S Afr Med J 1985;67:378-382. 4. Przybojewski JZ, Weich HFH. Percutaneous tronsluminol coronary angioplasty: o review of the Iiteroture. S Afr Med J 1984;65:(Jonuory):l-22. 5. Mehta J, Mehta P, Horalek C. The significance of platelet-vessel wall prostaglandin equilibrium during exercise-induced stress. Am Heart J 1983;105: 895-900.
CORONARY ANGIOPLASTY BALLOON COMPLIANCE AND TEMPERATURE The article by Jain et al1 addressed an important aspect of coronary balloon catheter angioplasty: the effective diameter of the different balloons at progressive inflating pressures. These data are essential for an appropriate choice of the balloon catheter and of the inflating pressure, z major determinants of the degree of relief of the stenosis, of the incidence of initial dissection and, probably, oftherestenosisrate.Theirconclusionswere: the Advanced Cardiovascular System (ACS) balloons are smaller at equal pressure of inflation and they have similar compliance to the polyvinyl chloride (USCI) counterparts1 As the daily experience in clinical angioplasty suggests a substantially different behavior of the z types of catheters, I compared the above data to those available from the catheter message,
manufacturers.z*s To simplify the the USC1 data2 indicate a relative
change of their 2.5-mm balloon (LPS-I] diameter of 12% (from 2.25 to 2.73 mm) when he inflation pressure is increased from 4 to 10