[Differential indication for coronary stent implantation. Comparative study of acute cardial and vascular complications in relation to the indication]

BACKGROUND AND OBJECTIVE

Coronary stents are used nowadays not only for the reduction of restenosis and for treating acute vessel occlusions after PTCA but also after acute myocardial infarction. This study was undertaken to determine whether widening the indications has affected the incidence of acute complications and to compare acute cardiac and vascular complications.

PATIENTS AND METHODS

The data on 197 consecutive patients (155 men, 42 women; mean age 62 +/- 9 [37-85] years) with coronary stents were analysed retrospectively, divided into 5 groups depending on the indications for the stent implantation: 1) acute or threatened vessel occlusion after elective PTCA ("bail-out"); 2) acute myocardial infarction (AMI); 3) unstable angina with threatened vessel occlusion; 4) suboptimal primary results (angiographically assessed) after PTCA; 5) elective stent implantation to prevent restenosis. Acute or subacute stent thrombosis, side-branch occlusion, intra- and transmural infarction, death and emergency aortocoronary bypass operation were classified as acute cardiac complications. Haemorrhage in the inguinal region requiring blood transfusion, false aneurysm and operative vascular reconstruction were classified as vascular complications.

RESULTS

An intended stent implantation was impossible in 18 patients (primary success rate 91%). Independent of indication an acute or chronic stent stenosis occurred in three (1.6%) and seven (3.9%) patients, respectively. Side-branch occlusion was observed in 12 patients (6.7%), transmural infarction in nine (5.6%). No emergency bypass operation had to be performed. Comparing the different indication groups there was a significantly increased rate of "non-Q" infarctions in patients with unstable angina pectoris (P < 0.014). Among acute vascular complications (10 [5%] inguinal haemorrhages requiring transfusion and 5 [2.5%] operative vascular reconstructions), false aneurysm was significantly more common in patients with AMI (P < 0.014). Comparing emergency and elective stent implantations, side-branch occlusions were significantly more common in the former (12% vs. 0%; P < 0.08), as were also "non-Q" infarcts (10% vs. 0%; P < 0.002).

CONCLUSION

Coronary stent implantation for these indications, including AMI, can be taken as firmly established. Stent thrombosis was not significantly increased after "bail out". Implantation in an acute ischaemic episode led to a significantly higher incidence of side-branch occlusion and "non-Q" infarction.

[Balloon dilatation in acute myocardial infarct in routine clinical practice: results of the register of the Working Society of Leading Cardiologic Hospital Physicians in 4,625 patients]

Balloon angioplasty as the treatment of first choice in the setting of an acute myocardial infarction (AMI) is gaining widespread acceptance because of favourable results from specialised centres concerning high patency rates and low mortality. This study reports the results of angioplasty for AMI at large community hospitals during 1992-1995. 4625 procedures were performed at 68 centres of the Arbeitsgemeinschaft Leitender Kardiologischer Krankenhausärzte (ALKK). The age of the patients was 60.8 +/- 11.3 years, with 75.1% men. The infarct related artery was the left anterior descendent in 43%, the right coronary artery in 37%, the circumflex artery in 16%, a bypass graft in 2.3% and the left main stem in 1.4% of patients. The success rate (residual stenosis < 50%) of the intervention was 86%. There was a wide range of procedures per centre, with a median of 40 AMI angioplasties per year and centre. The amount of angioplasties for AMI in relation to all angioplasties performed during this period rose from 5.2% in 1992 to 5.9% in 1995 (p = 0.01). Local complications at the puncture site occurred in 3.2%, with the need for a surgical intervention in 1.1% of patients. In 273 (5.9%) of the patients a second angioplasty was performed during the hospital stay. Aortocoronary bypass surgery was performed in 3% of the patients. Hospital mortality was 9.5% (438/4625 patients). The mortality rate remained constant during the years investigated (1992: 10.6%; 1993: 8.6%; 1994: 9.7%; 1995: 9.8%; p = ns). Higher mortality was observed in older patients, patients with multiple vessel disease, the left anterior descending artery or a bypass graft as infarct related artery as well as in patients with failed reperfusion (residual stenoses > 50%). Hospitals with a case load of more than 40 angioplasties for AMI per year showed a lower mortality as compared to the others. In clinical practice at large community hospitals results of angioplasty for AMI concerning mortality, complications and technical success rate are comparable to those of highly specialised centres. The absolute numbers of angioplasties for AMI increased constantly over the years.

Dobutamine stress echocardiography

Dobutamine is a synthetic catecholamine with predominant beta-stimulation. Its half-life is approximately 2 min. The positive chronotropic and inotropic effects of dobutamine induce myocardial ischaemia if significant coronary artery obstruction is present. Regional ischaemia produces regional wall motion abnormalities which can be detected by echocardiography. Most dobutamine stress protocols start at an infusion rate of 5 micrograms.kg-1.min-1 and increase to a peak dose of 40 or 50 micrograms.kg-1.min-1; to further increase heart rate, a bolus injection of 0.25-1.0 mg atropine is added. Test endpoints are the detection of new wall motion abnormalities, the occurrence of severe complications or achievement of the target heart rate. Viable myocardial regions have a positive inotropic reserve, which can be stimulated by dobutamine and detected by echocardiography. Indications for the use of dobutamine stress echocardiography are to prove stress-inducible myocardial ischaemia and to detect myocardial viability. The test should only be performed for the detection of stress-induced myocardial ischaemia if patients are unable to undergo exercise echocardiography, or if patients fail to reach their required test level in exercise echocardiography.

[Value of K+ and Mg2+ in treatment of acute myocardial infarct]

A critical role analysis of literature concerning the effects of intravenous magnesium on arrhythmias and mortality in acute myocardial infarction shows discrepant results and often inappropriate methods. So far neither an antiarrhythmic efficacy nor prophylactic effects with respect to mortality could be demonstrated. In contrast, potassium substitution should be performed in the setting of acute myocardial infarction with documented hypokalemia (K+ < 3.5 mmol/l) because of increased risk of ventricular arrhythmias. According to the documented results of the trials reviewed in this article no recommendations for the routine use of magnesium in myocardial infarction can be given.

Arbutamine stress echocardiography

Arbutamine, a new potent non-selective beta-adrenoceptor agonist with mild alpha 1-sympathomimetic activity, has been developed specifically for pharmacological stress testing. The drug acts like physical exercise, increasing both heart rate and myocardial contractility. Sensitivity, specificity and accuracy in detecting significant stenotic coronary artery disease are 76%, 96%, and 82%, respectively, again similar to those of exercise echocardiography. The drug is delivered by a computerized drug delivery and monitoring device (GenESA) which adjusts the infusion rate according to the patient's heart rate data feedback. The drug is generally well tolerated and has an acceptable safety profile. This article describes recent clinical experience with arbutamine and presents preliminary results of a multicentre multinational study which evaluates the clinical utility and safety of the GenESA system in diagnosing coronary artery disease.

Stress echocardiography: personnel and technical equipment

In recent years, stress echocardiography has gained broad acceptance as a non-invasive method for the diagnosis of coronary artery disease. Facing different protocols, dosages and instrumentation, official guidelines for the performance, standardization and quality control of stress echocardiograms are needed; however, so far they are not available. This paper recommends the type of personnel and technical equipment needed for stress echocardiography laboratories, based on experience gained during more than 2000 stress echocardiographic procedures. To perform stress echocardiography, a cardiologist and a technical assistant--both well trained over a large number of tests--should be involved. The laboratory must have basic equipment such as a 12-lead ECG, blood pressure monitoring capacity, a treadmill or bicycle for ergometry, a precision intravenous delivery system for pharmacological stress testing as well as an adequate echo table; additionally, emergency equipment is mandatory. The ultrasound machine should contain transducers with high 2-D resolution; most important is a digital image acquisition system which facilitates performance and interpretation through side-by-side display of synchronized rest and stress images. Finally, there is a need for proper patient preparation and the obtaining of informed consent.

Detection of myocardial viability using stress echocardiography

Asynergic myocardial regions in patients with coronary artery disease can be viable. They may have the ability to improve their function after restoring coronary blood flow. Asynergic but viable myocardial regions have a positive inotropic reserve which can be stimulated by catecholamines. Because echocardiography is an established method for evaluating regional left ventricular function, it has the potential to detect the inotropic response of asynergic myocardial regions. In the clinical setting, prediction of left ventricular functional improvement after revascularization is particularly important. Dobutamine stress echocardiography is the most frequently used stress echocardiographic test for detection of myocardial viability. Dobutamine is infused at low rates of 2.5 to 20 micrograms.kg-1.min-1 to detect myocardial viability. This paper reports on the sensitivity and specificity of the method for the detection of viability and its usefulness for prediction of left ventricular functional improvement after revascularization.

[Drug therapy of tachycardic atrial arrhythmias]

There are defined indications for the acute pharmacological management of AV-nodal reentry tachycardias, AV reentry tachycardias and for the acute and chronic ventricular rate control in atrial fibrillation. Possible indications arise for the chronic pharmacologic therapy of AV reentry tachycardias, pharmacological cardioversion and prophylaxis of atrial fibrillation. In future there will be a trend towards nonpharmacological management of atrial arrhythmias.

Primary angioplasty versus thrombolysis in the treatment of acute myocardial infarction. ALKK Study Group

This study investigates the hypothesis if primary angioplasty is superior to intravenous thrombolysis in the treatment of acute myocardial infarction (AMI). Small prospective randomized studies did not demonstrate a significant benefit regarding total mortality. A total of 14,980 patients with AMI were registered by "The 60-Minutes Myocardial Infarction Project," a prospective multicenter observational study: 210 of these patients were treated with primary angioplasty. A matched pair analysis comparing 1 primary angioplasty patient with 3 intravenous thrombolysis patients could be performed in 156 primary angioplasty patients. Criteria for matching were age, sex, location of AMI, systolic blood pressure, previous AMI, and prehospital delay. Patients with a bundle branch block or requiring resuscitation were excluded from analysis. Because of matching, both groups showed similar baseline characteristics. Patients with primary angioplasty had more relative contraindications for thrombolysis (ulcers: 10.3% vs 2.3%, recent intramuscular injections: 6.4% vs 1.6%, recent surgical interventions: 5.1% vs 1.1%, central punctures: 9% vs 3.9%). There was a tendency toward less combined adverse events in the primary angioplasty group (3.2% vs 5.7%, odds ratio [OR] = 0.55, 95% confidence interval [CI] = 0.21 to 1.44). In-hospital mortality rates in the primary angioplasty group and thrombolysis group were 4.3% and 10.3%, respectively (OR = 0.39, 95% CI = 0.17 to 0.92). The difference in mortality could already be demonstrated within the first 48 hours with 1.9% versus 5.3% deaths (OR = 0.35, 95% CI = 0.11 to 1.14). Thus this study indicates a superiority of primary angioplasty in comparison to intravenous thrombolysis in AMI even in a clinical routine setting, with a reduction of hospital mortality of about 60%.

-Value of activated blood coagulation time in monitoring anticoagulation during coronary angioplasty-

Accurate heparin anticoagulation assessment is important to prevent complications (hemorrhage, thrombotic coronary occlusion) during and after coronary angioplasty (PTCA). Paired ACT-, aPTT- and prothrombin time (PT) measurements have not been studied after PTCA using a high dose heparin management. For that reason we analyzed in 150 consecutive patients (115 m., 35 f., 61 +/- 10 y.) immediately after PTCA and at the time of arterial sheath removal aPTT-(Neothromtin, Behring), PT- (Thromborel S, Behring) and ACT-(HR-ACT, HemoTec) values after application of 20,000 U of heparin (5,000 U intravenous, 15,000 U intracoronary) followed by a heparin-infusion (15,000-25,000 U/24 h). Immediately after PTCA in all patients a aPTT above the upper limit of >180 s was found. The average postprocedural ACT was 330 +/- 82 s. Only 9 patients showed an ACT below 200 s. All coronary reocclusions (n = 3) immediately after PTCA occurred in this group. Arterial sheaths were removed 13 +/- 3 h after PTCA. The incidence of minor peripheral bleeding complications at that time was 21% and was related to the anticoagulation level. Major bleeding complications requiring transfusion were noted in only one case. Our findings suggest that after high dose heparinization for PTCA the ACT test provides a reliable and broad range for the assessment of heparin anticoagulation. In contrast to the aPTT the ACT is ideally suited to determine the dosage of heparin infusion and the time of arterial sheath removal after PTCA. ACT measurements are superior to aPTT measurements in heparin anticoagulation assessment during and direct after PTCA.

[Inpatient length of stay and physical capacity after aortocoronary bypass operation, after heart valve replacement and myocardial infarct]

The present investigation was performed to determine the dependence of the length of stay in community hospitals and rehabilitation clinics from patient characteristics and physical activity at the end of treatment. Comparing age, end-diastolic volume index, left ventricular ejection fraction, number of stenosed coronary arteries, number of bypass grafts, levels of physical exercise, body mass index and the ratio total cholesterol/HDL-cholesterol, no significant differences were found in patients, who reached the rehabilitation clinic in the early postoperative period (7.4 +/- 2.0 days, n = 98), after 15-28 days (n = 74) or later than 28 days (n = 156) after bypass-surgery. Similar results were observed in 103 patients after heart-valve replacement, who arrived at the rehabilitation clinic after a corresponding length of hospital care like the bypass patients. Also, no significant differences in the clinical characteristics and physical activity appeared in patients who were admitted in the early phase (9.2 +/- 4.5 days) after transmural myocardial infarction (n = 37) and those entering the rehabilitation clinic after 26.7 +/- 9.4 days of hospital stay (n = 32). The absence of any relationship between the length of stay in hospitals on the one hand and severity of the heart disease on the other hand points out that the whole duration of stay in community hospitals and rehabilitation clinics after surgical intervention and also after transmural myocardial infarction could be drastically shortened by an optimal cooperation of both, hospitals and rehabilitation clinics, without any impairment of clinical results.

Cardiogenic shock in acute myocardial infarction. Improving survival rates by primary coronary angioplasty

This study reports on 16 patients suffering from cardiogenic shock in the setting of acute myocardial infarction (11 men, five women; average age: 52.5 +/- 14 years) treated by means of primary coronary angioplasty: These 16 patients were part of a total population of 261 patients suffering from acute myocardial infarction at the time of admittance to the Wuppertal Heart Center, who were consecutively treated during the period from 1/90 to 6/94 by primary coronary angioplasty without having received any prior thrombolytic therapy. For all patients, primary re-opening of the vessel infarcted was successful. The period of time between onset of pain until re-opening of the vessel averaged 176 +/- 49 min. Eleven patients suffered from multi-vessel coronary artery disease. Prior to re-opening, systolic blood pressures averaged 66 +/- 10 mm Hg; average biplan left ventricular ejection fraction, 40 +/- 12%; left ventricular end-diastolic pressures (LVEDP), 26 +/- 7 mm Hg. In 63% of the cases evaluated, it proved possible to document collaterals to the infarcted vessel. Thirteen patients survived acute coronary occlusion. Two patients died due to protracted myocardial pumping failure, despite re-opened arteries that effectively re-established coronary flows. Showing symptoms of re-occlusion, one patient developed electromechanical decoupling. Thirteen patients were discharged from the hospital for normal life or subsequent treatment. Overall, this corresponds to an in-hospital survival rate of 81%. During follow-up examinations performed over 14 +/- 8 months (range 3 to 30 months), all of the patients are alive. Mean left ventricular ejection fraction increased to 56% +/- 17%; mean left ventricular end-diastolic pressure dropped to 14 mm Hg +/- 5 mm Hg. In the infarct-related artery there was no recurrence of stenoses exceeding 50%. By now, one of the patients has received elective aorto-coronary bypass grafting; for another one, multi-vessel PTCA of non-infarcted arteries is being employed; 77% of the patients state that they are satisfied with the quality of their lives. These results demonstrate that rapid revascularization using coronary angioplasty in cardiogenic shock following acute myocardial infarction substantially improves the prognosis for survival and favorably influences long-term outcome. Thus, primary PTCA is the method of choice for treating cardiogenic shock; any patient-and particularly those resistant to lyse therapy-should immediately receive this treatment.

[Successful high frequency current catheter ablation of an accessory conduction pathway in the "neck region" of a coronary sinus aneurysm. A case report]

In this case report the electrophysiological findings in a 24 year old female patient are demonstrated. For about 12 years she suffered from recurrent atrioventricular reentrant tachycardia with a rate of 230 beats per minute. Electrophysiological study resulted in diagnosis of a posteroseptal accessory pathway. Ablation was attempted primarily from a left ventricular access, but the pathway could not be reached from this position. After contrasting the coronary sinus a large coronary sinus aneurysm could be diagnosed. The accessory pathway was located in the "neck"-region of the aneurysm. By application of radiofrequency current in this location the bypass tract could be ablated. This case report shows that accessory pathways in coronary sinus aneurysms can be ablated without complications in this location.

Left ventricular malposition of a transvenous cardioverter defibrillator lead: a case report

A case of left ventricular endocardial malposition of a transvenous implantable cardioverter defibrillator (ICD) lead through a patent foramen ovale is presented. Diagnostic modalities include lateral chest radiography, echocardiography, and electrocardiographic analysis during lead placement. The operative therapy consists of open lead replacement. Measures to avoid lead misplacement are suggested.

[Biophysical aspects of high frequency catheter ablation. Studies of the significance of sudden changes in impedance]

To determine the effects and the underlying mechanisms of sudden rise of impedance during radiofrequency (RF) catheter ablation, 60 RF applications were delivered to isolated preparations of ventricular myocardium at three different power levels (mean: 3.7, 11.3, 19.3 watts). Pulse duration was 30 s, current voltage and catheter tip temperature were continuously monitored. Impedance rise occurred during 34 of 60 applications; the incidence of impedance rise increased at higher power levels. Impedance rise was significantly more often observed when the preparations were superfused with heparinized blood compared to saline solution (p less than 0.05). Catheter-tip temperature during radiofrequency application without impedance rise was significantly lower compared to applications with impedance rise (mean = 108 degrees C vs. 121 degrees C, p less than 0.01). The increase of catheter-tip temperature and maximal-tip temperature following impedance rise was significantly higher in blood when compared to saline solution (mean = +48 degrees C vs. +13 degrees C (p less than 0.001), Tmax: 121 degrees C vs. 245 degrees C). Following impedance rise, insulation defects of the electrode catheter and vaporized crater formation of the myocardium was often observed.

CONCLUSIONS

During radiofrequency catheter ablation impedance rise occurs following overheating of the catheter electrode (greater than 110 degrees C). After impedance rise, catheter-tip temperature markedly increases. Insulation defects of the catheter and vaporized craters in the myocardium frequently occur after impedance rise. The results have important implications for the clinical use of RF-currents for catheter ablation; energy application should be immediately stopped after the occurrence of impedance rise.

[Left atrial myxoma]

Left-atrial myxomas produce a broad array of clinical symptoms depending on their location, size, and morphology. The clinical presentation is characterized by obstruction of blood flow, systemic embolism, and unspecific systemic effects. Within 6 weeks, three patients presented in our clinic with left-atrial myxomas. Primary differential diagnoses were infective endocarditis, circulatory collapse, and transient ischemic attack of unknown origin. In all cases diagnosis was made with echocardiography (m-mode, 2D, TEE). In this review the etiology, epidemiology, and pathology are reported briefly. The variety of clinical symptoms with the corresponding differential diagnosis is presented systematically and discussed with our patients. Diagnostic, therapeutic, and prognostic aspects are summarized.

Nd: YAG Laser-Photocoagulation: Acute Electrophysiological, Hemodynamic, and Morphological Effects in Large Irradiated Areas

Laser-photocoagulation (LPC) of arrhythmogenic myocardium has been reported to successfully ablate ventricular tachycardia. The purpose of this study was to investigate the acute hemodynamic and electrophysiological effect of continuous laser energy (Nd:YAG, 1060 nm) applied via a 0.4-mm quartz fiberoptic on the epicardial surface of the heart in nine dogs. A total of 51 +/- 2.3 pulses was delivered in each animal to induce homogeneous tissue necrosis. Applied energy was 12.3 +/- 2.7 J/mm2, irradiated surface measured 12.6 +/- 3.0 cm2, lesion depth was 6.3 +/- 1.2 mm (range: 5.0-8.1 mm), lesion volume was 8.1 +/- 2.8 cm3 (6.8% of left ventricular [LV] mass). After LPC, epicardial stimulation threshold significantly rose from 1.0 +/- 0.3 to 10.2 +/- 4.9 mA in the border zone to nontreated tissue and from 0.9 +/- 0.4 to 32 +/- 15.7 mA in the center of the lesions. Loss of epicardial activation in the irradiated areas could be demonstrated by epicardial mapping. Ventricular extrasystoles during LPC were seen in all dogs, ventricular tachycardia in seven, and ventricular fibrillation in two dogs. After LPC, cardiac output and LV dP/dtmax significantly decreased by 14.2% and 11.2%. LPC induced predictable homogeneous tissue edema, eosinophilic staining, contraction band necrosis, and sharp demarcated hemorrhagic border zones with a sharp electrical border zone to nontreated tissue and loss of epicardial activation. During LPC, various arrhythmogenic effects could be observed. However, no persistent arrhythmic activity developed after LPC. The results confirm the feasibility of epicardial LPC of the myocardium. Although not rested in this study, LPC of arrhythmogenic tissue may also be feasible as a treatment modality of ventricular tachycardia.

[Percutaneous endocardial Nd-YAG laser energy: experimental studies of ablation of the ventricular myocardium]

The in vitro and in vivo effects of endocardial laser ablation were assessed. Energy was supplied by a Nd-YAG laser (wavelength approximately 1064 nm) and transmitted via a quartz core fiber (phi: 0.4 mm) housed within a specially designed 7 F catheter. In vitro, the effects of increasing output power (5, 10, 20, 40 watt) and impulse duration (1, 2, 4, 8 s) on lesion size were assessed in myocardial preparations of canine hearts. Preparations were superfused with saline or blood, respectively; the distance of the optical fiber to the endocardium was 5 mm. Lesion size increased in diameter (range: 0-4.0 mm) and depth (range: 0-5.2 mm) in a power- and time-dependent manner. Superfusion with blood significantly enhanced the diameter of the lesions, whereas depth of the lesions significantly decreased. In 16 anesthetized mongrel dogs, a total of 52 laser impulses (output power: 10, 20, 40 w; impulse duration: 1, 2, 4 s; energy: 10-160 J) were delivered to apical and apico-inferior sites of the left ventricle. Postmortem, 40 lesions with a diameter of 2.6-19.4 mm and a depth of 3.7-16.2 mm were found. 19 lesions revealed central vaporized craters with a depth up to 11.2 mm. Perforation of the left ventricle occurred in two cases following 80 and 160 J, respectively. In vitro and in the intact animal (in apical and apico-inferior sites of the left ventricle) endocardial laser ablation is feasible to induce distinct myocardial lesions in a power- and time-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Constant-flow ventilation during experimental left ventricular failure

The efficacy of constant-flow ventilation (CFV) was investigated in dogs with normal heart function (control phase, n = 8) and after development of left ventricular failure (LVF phase, n = 8). Heated, humidified and oxygen-enriched air (inspired oxygen fraction (Fio2) = 0.4) was continuously delivered via two catheters positioned within each mainstem bronchus at two flow rates (1.2 and 1.6 l/kg/min). Conventional mechanical ventilation (CMV) with positive end-expiratory pressure (PEEP) of 0.5 kPa was used as reference ventilation. During control, neither CMV with PEEP nor CFV revealed severe impairment of cardiopulmonary performance. Alveolo-arterial PO2 difference (P(A-a)O2) increased significantly during CFV1.2 and CFV1.6, indicating a higher degree of ventilation-perfusion (VA/Q) inhomogeneity. Acute left ventricular failure (LVF) was induced by proximal occlusion of the left anterior descending (LAD) coronary artery. Cardiac output (CO), maximum velocity of pressure development (dP/dtmax) and mixed venous PO2 decreased (P less than or equal to 0.05), whereas left ventricular end-diastolic pressure (LVEDP) and pulmonary capillary wedge pressure (PCWP) increased (P less than or equal to 0.05). Extravascular lung water (EVLW), as determined by thermal-dye technique, increased from 10.1 ml/kg to 20.9 ml/kg (P less than or equal to 0.01). Oxygenation, but not CO2 elimination, deteriorated in the LVF phase. There were no haemodynamic differences between CMV with PEEP and CFV1.2, but cardiopulmonary performance deteriorated with CFV1.6. Gas exchange was significantly more impaired during CFV1.2 and CFV1.6 due to increased VA/Q mismatching. However, there were no significant differences for P(A-a)O2 values between CFVControl and CFVLVF.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiofrequency coagulation of ventricular myocardium: improved prediction of lesion size by monitoring catheter tip temperature

To assess the importance of voltage, current, impedance and catheter tip temperature for the prediction of the size of tissue injury induced by transcatheter radiofrequency application, radiofrequency pulses (500 kHz) were delivered both in vitro and in vivo to isolated ventricular preparations and the intact canine heart, respectively. Radiofrequency coagulations were performed using unipolar electrode configuration. Besides measurements of current and voltage which were used to calculate the delivered power and tissue impedance, the catheter tip temperature was monitored during each application using specially designed 6F USCI catheters with a built-in nickel/chromium-nickel thermoelement. Lesion dimensions were measured and the correlation between lesion volume and delivered radiofrequency energy, maximum changes in catheter tip temperature and the integral of the temperature curve were calculated. First, in a pilot in vitro investigation, 50 radiofrequency coagulations (3.2 W-22.4 W, pulse duration 10 s) were performed in ventricular preparations from freshly excised dog hearts. The correlation between applied radiofrequency energy and lesion volume was 0.87; the correlation between maximal catheter tip temperature and lesion volume was 0.82; the correlation between temperature integral and lesion volume was 0.9. In the intact dog heart, 44 radiofrequency pulses were delivered to the left and right ventricular endocardium in 12 anaesthetized dogs (exposure time: 10 s). Delivered power ranged between 5.6 W and 24.6 W; tissue impedance varied between 92 omega and 364 omega; lesion volume measured 0-273 mm3; developed peak temperatures ranged from 16.25 degrees C to 196 degrees C. The calculated integral beneath temperature curves measured 126-1971 degrees C.s. The correlation between applied radiofrequency energy and lesion volume was 0.32; the correlation between maximal catheter tip temperature and lesion volume was 0.61. Temperature integral correlated best with the assessed volume of myocardial necrosis (r = 0.7). No significant arrhythmogenic or haemodynamic side-effects were observed. Macroscopic examination showed a central depression surrounded by a zone of homogeneous coagulation. Vaporization and crater formation up to a depth of 4 mm were observed following three radiofrequency discharges. In two of these cases, rapid changes and oscillation of catheter tip temperature were observed. Thus, monitoring of catheter tip temperature during radiofrequency energy application improves the prediction of lesion size. In addition, temperature monitoring might improve the safety of the procedure with respect to the risk of perforation.

Electrophysiologic, haemodynamic and antiarrhythmic effects of the new class Ic agent 1-(2'-biphenyloxy)-2-tert.-butylamino-propanol-2-hydrochloride

The electrophysiological, antiarrhythmic and haemodynamic profile of the new compound GK 23-G (1-(2'-biphenyloxy)-2-tert.-butylamino-propanol-2-hydrochloride, proposed INN: bipranol) was examined using dogs models relevant to conditions in humans. In the first part of the study, dose-related effects of cumulatively increasing doses of GK 23-G (0.2-12.8 mg/kg) on intracardiac conduction, ventricular refractoriness and on haemodynamic parameters of the non-ischemic heart were determined in six anesthetized mongrel dogs. In the second part of the study, antiarrhythmic actions of bipranol on "delayed reperfusion ventricular arrhythmias" following release of coronary artery occlusion after 2 h of obstruction were investigated in another six dogs. The results show: GK 23-G causes a significant prolongation of HV-time, QRS-duration and ventricular refractory period at mid-range and high doses (greater than or equal to 3.2 mg/kg). QT-time does not change. Atrial refractory period is significantly lengthened at the maximum dose of 12.8 mg/kg. There are no significant changes in heart rate, systolic and diastolic aortic pressure and cardiac output. Up to 12.8 mg/kg, GK 23-G does not influence left ventricular contractility (dp/dtmax). In acute myocardial necrosis "delayed reperfusion arrhythmias" are almost completely abolished at a dose of 1.6 mg/kg + 50 micrograms/kg x min. Thus, because of its antiarrhythmic potency, further experimental and clinical testing of the new compound seems promising.

[Ion regulation disorders and cardiac arrhythmia. The relevance of sodium, potassium, calcium, and magnesium]

1. Among the dysionemias hyper- and hypokalemia are particularly important for clinical arrhythmogenesis. Disorders in sodium- and calcium concentrations, however, are relevant only in single cases. The impact of magnesium concentration disorders on cardiac rhythm is not yet totally elucidated. 2. In hypokalemia tachycardic arrhythmias are most important, while bradycardic and tachycardic arrhythmia can be caused by hyperkalemia. An important factor in arrhythmogenesis is the rate of development of hypo- or hyperkalemia. Hypokalemically-induced arrhythmia can be suppressed by potassium substitution. 3. Although the importance of a magnesium dysionemia for arrhythmogenesis has not been confirmed, magnesium can be used for the treatment of arrhythmias with good results. Besides an antiarrhythmic efficacy, an antifibrillatory activity is suggested in acute myocardial ischemia.