Matthias Sturm

Effects of Intracardiac Radiofrequency Current Application on Coronary Artery Vessels in Young Pigs

Radiofrequency Current Lesions in Young Pigs. Introduction: Radiofrequency current is widely used in children to ablate accessory AV pathways. Previous data in a pig model demonstrated coronary artery obstruction adjacent to radiofrequency current lesions 48 hours and 6 months after energy delivery. In the present study, the long‐term effects (>6 months) of radiofrequency current application on coronary artery vessels in young pigs are assessed.

Comparison of different quantitative coronary analysis systems: ARTREK, CAAS, and CMS

It has been known that the first generation quantitative coronary analysis systems overestimate small vessel sizes. In the 2nd generation the contour detection algorithms, e.g., of the new Cardiovascular Measurement System (CMS), were modified to correct for the limited resolution of the X-ray imaging chain. This study validated and compared the CMS with the well-known Coronary Angiography Analysis System (CAAS) and the vessel tracking program ARTREK in a phantom study and a clinical study. In addition, the influence of different acquisition media (cinefilm vs. digitally acquired angiograms) on the accuracy of quantitative analysis was examined. The phantom study comprised 19 stenotic or non-stenotic glass tubes with a diameter range from 0.54 mm to 4.9 mm. In the clinical study the mean diameters of 322 coronary segments were analysed and the results of the systems were compared among each other. The results of the phantom study were presented in terms of the mean difference (accuracy) between true and measured values. In the phantom study the overall accuracy of the CMS was -6 microns (ARTREK: 85 microns; CAAS: 35 microns) with an overestimation of small vessels of only -11 microns (ARTREK: 97 microns: CAAS: 51 microns). The clinical study showed that the CMS corrected the usually occurring overestimation of small coronary arteries and that the influence on the accuracy of different acquisition media is minor. Due to the modified algorithms the new CMS is able to measure coronary diameters down to 0.5 mm accurately. Therefore, the CMS seems to provide more precise measurements in quantitative analysis of small coronary diameters than CAAS and ARTREK.

How to standardize vasomotor tone in serial studies based on quantitation of coronary dimensions

In patients with coronary artery disease including those after coronary bypass graft operation and heart transplantation intervention studies based on serial quantitative coronary angiography, in part combined with intravascular ultrasound, are of increasing relevance. Since vasomotor tone of epicardial coronary arteries is influenced by a variety of factors, angiographic follow-up studies require standardization of coronary tone by induction of maximal dilation. We reviewed the effects of the most potent coronary vasodilatory drug groups, calcium antagonists and nitrocompounds, on coronary diameters. Intravenous or intracoronary injections of verapamil, diltiazem, nifedipine, nicardipine, and nisoldipine can cause profound coronary dilation which has been shown to be maximal with verapamil and nisoldipine. Shortcomings of calcium antagonists include short or unknown duration of action after bolus administration, severe drop in blood pressure, and lack of commercial availability of solutions for injection of many substances. Isosorbide dinitrate induces profound coronary dilation; however, after sublingual administration marked blood pressure decrease can occur, and the duration of action and ideal dose of intracoronary isosorbide dinitrate has not been investigated yet. Injections of molsidomine and its active metabolite, SIN-1, cause longlasting, reproducible, maximal coronary dilation, although only after a waiting period of at least 10 minutes; unfortunately, SIN-1 is only commercially available in France. Nitroglycerin induces reproducible maximal coronary dilation and is easy to administer sublingually or as intracoronary bolus injection with rapid onset of action and no major side effects. The short duration of action may require repeated administrations. To date, repeated intracoronary bolus injections of 0.1 mg nitroglycerin every 10 minutes seem to be the optimal known regimen for standardization of coronary vasomotor tone in serial angiographic studies. Further investigations in this field with old and new vasodilatory drugs are recommendable.

Incidence and time course of intimal plaque formation in the right coronary artery after radiofrequency current application detected by intracoronary ultrasound

Die Hochfrequenzstromablation gehört heute bei Kindern und Jugendlichen zum klinischen Standard. Allerdings sind die Spätfolgen der Energieapplikation am unreifen Myokard bislang unbekannt. Ziel der vorliegenden tierexperimentellen Untersuchung war es, die Häufigkeit und Manifestation von Läsionen der Koronararterien nach Hochfrequenzstromapplikation am unreifen Myokard darzustellen. Bei 10 jungen Schweinen (Alter im Mittel 6 Wochen, Gewicht im Mittel 13±2 kg) wurde Hochfrequenzstrom (500 kHz) mit einer Zieltemperatur von 75 °C über einen steuerbaren Elektrodenkatheter mit einer 4 mm-Spitzenelektrode über die Dauer von jeweils 30 s appliziert. Hochfrequenzstromläsionen wurden am lateralen rechten Vorhof unmittelbar am Trikuspidalklappenanulus sowie am lateralen linken Vorhof und linken Ventrikel unmittelbar am Mitralklappenanulus erzeugt. Alle Tiere wurden mittels selektiver Koronarangiographie sowie intrakoronarem Ultraschall der rechten Koronararterie (RCA) sowie des Ramus circumflexus (CX) 3, 6, 9 und 12 Monate nach der Energieapplikation nachuntersucht. Mit der quantitativen Koronarangiographie fanden sich keine Hinweise für signifikante Stenosen der beiden Gefäße. Initimaplaques der RCA (Fläche im Mittel 2,2±0,2 mm2, Lumeneinengung im Mittel 30,4±4%) wurden mit dem intrakoronaren Ultraschall erstmals 6 Monate nach der Hochfrequenzstromapplikation nachgewiesen. Das Ausmaß der Plaques zeigte sich in den nachfolgenden Untersuchungen unverändert. Bei allen 3 Tieren wurden die Stenosen der RCA im Rahmen der histologischen Untersuchungen 12 Monate nach der Energieabgabe bestätigt. Stenosierungen der RCA als Spätfolge der Hochfrequenzstromapplikation an der lateralen Vorhofwand wurde bei 3 der 8 langzeitüberlebenden Tiere nachgewiesen. Der Zeitrahmen für die Manifestation dieser Stenosen erstreckt sich über den Zeitraum von 3 bis 6 Monaten nach der Energieabgabe. Mit der selektiven Koronarangiographie konnten die Stenosen der RCA nicht dargestellt werden. Das Risiko der Entwicklung von Stenosierungen der Koronararterien sollte bei der Indikationsstellung zur Hochfrequenzstromablation bei Säuglingen und Kleinkindern beachtet werden. Despite the current clinical use of radiofrequency (RF) catheter ablation in infants and children, the late effects of RF current application at immature myocardium remain unclear. The purpose of this study was to investigate incidence and time course of coronary lesions after RF current application at developing myocardium in an animal model. In 10 pigs, 6 weeks of age (13±2 kg), RF current (500 kHz) was delivered by temperature guidance (75 °C) using a steerable electrode catheter (4 mm tip electrode) over 30-second periods. RF lesions were created at the lateral right atrial wall at the tricuspid valve annulus and the lateral left atrial and ventricular wall at the mitral valve annulus. Subsequent coronary angiography and intracoronary ultrasound (ICUS) of the right coronary artery (RCA) and the left circumflex artery (CX) were performed 3, 6, 9 and 12 months after RF current application. Quantitative coronary angiography did not exhibit any significant stenosis of the vessels during the study period. Intimal lesions of the RCA were documented for the first time at the 6-month study in 3 animals by ICUS (mean plaque area 2.2±0.2 mm2, mean area stenosis 30.4±4.0%). There was no significant change in lesion length, area stenosis and plaque area at the 9- and 12-month studies. All 3 coronary artery lesions were confirmed in close proximity to myocardial RF lesions by histological examination 12 months after RF delivery. No intimal plaque formation of the CX was observed. Affection of the RCA as a late sequel after RF current application at the lateral right atrial wall occurred in 3 out of 8 long-term surviving pigs. Three to six months seem to be the time frame for the development of intimal lesions after RF delivery. In this experimental setting, angiography failed to detect these intimal changes. The potential risk of coronary affection may be important for catheter ablation procedures at the right atrial myocardium in infants and small children.

Dislodgement of a Wiktor Stent during Intracoronary Ultrasound Examination

We report a case of stent dislodgement complicating adjuvant intracoronary ultrasound (ICUS) imaging that required emergency coronary bypass grafting. This probably very rare complication gains importance since ICUS is increasingly used to confirm adequate stent expansion and full coverage of the lesion.

Incomplete Expansion of Palmaz-Schatz Stents despite High-Pressure Implantation Technique: Impact on Target Lesion Revascularization

Improved expansion of stents using high-pressure implantation technique with subsequent antiplatelet therapy has improved patient outcome regarding the incidence of subacute stent thrombosis, bleeding complications and restenosis. Whether high-pressure implantation per se guarantees adequate stent expansion remains unclear. The aim of the study was to determine (1) stent expansion after high-pressure implantation technique and (2) whether stent expansion influences rate of target lesion revascularization within 6 months of follow-up. One hundred Palmaz-Schatz stents were implanted in 98 lesions (91 native vessels, 7 graft vessels) of 94 patients using high-pressure implantation technique (balloon pressure 12–20 atm). Stent expansion was investigated using intravascular ultrasound imaging (IVUS). Clinical follow-up of the patients was performed for 6 months. After implantation, stent/mean reference ratio was 0.81 ± 0.16. Noncompliant balloons used for implantation were chosen by angiographic criteria. Mean balloon/reference ratio was 1.08 ± 0.22; therefore balloons were not undersized. Additional balloon dilataion using higher pressures and/or larger balloons based on IVUS criteria and subsequent IVUS measurements was performed in 52 patients (55%); in these patients, stent expansion improved from 79 ± 16 to 91 ± 15% (mean ± SD) of average reference areas (p < 0.002). Within the 6 months’ clinical follow-up, target lesion revascularization was performed in 19 patients (20%). The only prognostic factors for the development of in-stent restenosis requiring target lesion revascularization were the vessel size (p < 0.05) and the extent of plaque distal to the stents (p < 0.05). Implantation of Palmaz-Schatz stents using high-pressure technique does not guarantee adequate stent expansion. Additional dilatation with higher pressures and/or larger balloons improves stent expansion. The size of the stented vessel and the extent of plaque at the distal stent end (residual outflow stenosis) but not the degree of stent expansion were predictors for target lesion revascularization within 6 months’ follow-up.

Acute Effects of Celiprolol on Angiographically Normal and Stenotic Coronary Arteries

Unselective and β_1-selective beta-blockers may induce vasoconstriction of normal and stenotic epicardial coronary arteries. To analyze the influence of the vasodilatory beta-blocker celiprolol on coronary vasomotility, 0.4 mg celiprolol/kg were intravenously infused over 4 minutes in 13 patients with coronary artery disease. Coronary angiograms were taken before (control) and at 4, 6, 8, 10, 15, and 20 minutes after the onset of infusion and 4 minutes after final sublingual administration of 0.4 mg nitroglycerin. Quantitative analysis of cinefilms demonstrated no significant diameter changes in angiographically normal coronary segments and stenoses. The vasodilatory capacity of normal segments (18 ± 12%; p ` 0.001) and stenoses (17 ± 14%; p ` 0.01) was proven by nitroglycerin. Systolic blood pressure, heart rate, and pulmonary wedge pressure revealed no significant changes with celiprolol. Thus, celiprolol exerts no vasoconstricting effects on angiographically normal and stenotic coronary arteries.

Angiographically undetected plaque in the left main coronary artery

The absence of angiographic findings despite significant coronary artery disease has been previously described. Possible explanations for the limitation of plaque detection by angiography include compensatory vessel enlargement in face of intracoronary plaque formation, the lack of reference segments in diffuse atherosclerosis as well as technical limitations. Intracoronary ultrasound (ICUS) imaging provides the possibility of direct plaque visualization. We studied angiographically normal left main coronary arteries (LMCA) in 72 patients prior to diagnostic angiography or therapeutic interventions using ICUS (30 MHz). ICUS images were continuously recorded and recalled from memory for morphometric analysis. Lumen area, plaque area and the total vessel area were determined by computer software. ICUS imaging revealed atherosclerotic plaque in 55 of the 72 patients with angiographically normal LMCA (76%). The average plaque area stenosis was 22±12% (range 3–44%). Total vessel area showed a significant direct correlation with plaque area, indicating compensation of coronary plaque formation. The average percent change in plaque area (difference between maximal and minimal plaque area within the LMCA) was 11±19%, indicating a diffuse pattern. Measurement of change in lumen area (difference between maximal and minimal lumen area within the LMCA) revealed an average value of 6±7%. Lumen area of the LMCA was 15.9±3.2 mm2 in patients with and 17.2±1.9 mm2 without atherosclerotic plaque (n.s.). Thus, the lack of angiographic changes despite advanced plaque formation in the LMCA could be explained by compensatory vessel enlargement and by diffuse distribution of plaque in the vessel; true lumen narrowings overlooked by angiography seem not to account for the failure of angiography to detect plaque.