Thomas Aretz

Echocardiographic measurement of right ventricular volume.

The volume of the right ventricle can be determined angiographically from its projections in two mutually perpendicular planes. Echocardiographic techniques for measuring right ventricular volume, however, have been more difficult and less successful. In this study, a method was developed for calculating right ventricular volume from two intersecting cross-sectional echocardiographic views: the apical four-chamber and subcostal right ventricular outflow tract views. First, the areas and lengths of casts of 12 human right ventricles obtained at autopsy were directly measured in the chosen views. Actual cast volumes correlated best with a formula giving volume as 2/3 times the area in one view times the long axis in the other view. The degree of correlation was similarly high for calculations involving the area derived from either view and the length of the roughly orthogonal section. This relationship for right ventricular volume was then confirmed with two-dimensional echocardiographic images of hollow latex molds made from the casts (r = .95, p less than .0001). The significance of these findings is discussed in relation to angiographic results and models of the right ventricle.

Feasibility of Radiofrequency Powered, Thermal Balloon Ablation of Atrioventricular Bypass Tracts Via the Coronary Sinus: In Vivo Canine Studies

Radiofeequency catheter ablation of left sided accessory pathways is technically demanding and usually requires left heart catheterization. The feasibility of creating lesions from within the coronary sinus of sufficient size to ablate accessory pathways in humans using a thermal balloon catheter was studied in 20 dogs. In group 1 (n == 14), 17 thermal inflations were performed in 12 dogs at either 70°, 80°, or 90°C each for 30 or 60 seconds (in 2 dogs two non‐thermal control inflations were performed). Animals were sacrificed 6.3 ± 1.6 days later. In group 2 (n = 6), seven thermal inflations were performed at 90°C each for 180, 300, or 360 seconds. Group 2 animals received antiplatelet and anticoagulant therapy for 1 week and were sacrificed at 13 ± 10.7 days. In both groups, hemodynamic, angiographic, and electrocardiographic studies were performed at baseline, 1 hour after inflation, and prior to sacrifice. All dogs remained clinically stable throughout the procedure and no complications were attributed to the effect of thermal inflation. Thermal lesions measured 14.4 ± 4.4 mm in length and extended from the coronary sinus intima to a mean depth of 2.9 ± 1.2 mm (range 1.4‐6.5 mm). Group 2 lesions were significantly deeper than group 1 lesions (P = 0.03). Of the 24 thermal lesions created, atrial necrosis was present in 23 and ventricular necrosis in 11. In all lesions there was some degree of either atrial necrosis, ventricular necrosis, or both. A variable degree of coronary sinus thrombus was present in 18 dogs without clinical sequelae. It is concluded that radiofrequency balloon heating via the coronary sinus can create thermal lesions in the atrioventricular sulcus of dogs that may be of sufficient size to ablate accessory left‐sided pathways in humans. (PACE 1995; 18: 1518‐1530)

Localized intramural drug delivery during balloon angioplasty using hydrogel-coated balloons and pressure-augmented diffusion

OBJECTIVES This study was designed to assess the feasibility of using hydrogel-coated balloons to deliver biologically active agents to the blood vessel wall. BACKGROUND The local intramural delivery of therapeutic agents during balloon angioplasty has been proposed as an adjunctive technique for preventing early intracoronary thrombosis and late restenosis. METHODS To assess the efficacy of delivery and depth of penetration in vitro, local delivery of horseradish peroxidase was performed in 40 porcine peripheral arteries, and delivery of fluoresceinated heparin was performed in 20 porcine peripheral arteries and 7 human atheromatous arteries. To determine the persistence of these agents in the vessel wall in vivo, horseradish peroxidase was delivered to 18 porcine peripheral arteries that were harvested at intervals of 45 min to 48 h. Fluoresceinated heparin was delivered to 22 porcine peripheral arteries, 14 with the use of a protective sleeve, harvested at intervals of 30 s to 24 h. RESULTS In vitro agent delivery was successful in all specimens. The depth of penetration of horseradish peroxidase was directly related to both balloon pressure (p < 0.04) and duration of inflation (p < 0.01). In vivo peroxidase staining was evident at 45 and 90 min but not thereafter. With the use of a protective sleeve, heparin was present in all arteries harvested at 30 s, with marked dissipation at 1 and 24 h. Without a sleeve, no fluorescein staining was detected in any artery. With both agents, delivery occurred consistently over broad regions of the vessel wall that were free of architectural disruption. CONCLUSIONS Hydrogel-coated balloons can deliver biologically active agents to the vessel wall without gross tissue disruption and may provide an atraumatic method for the local delivery of therapeutic agents during balloon angioplasty.

Method for estimating right ventricular volume by planes applicable to cross-sectional echocardiography: correlation with angiographic formulas

Right ventricular (RV) volumes determined by echocardiography were compared with those measured using established angiographic formulas. RV cast displacement volumes were first correlated with data derived from radiographic images of the casts corresponding to standard angiographic RV views. Four established angiographic formulas (Ferlinz, Boak, Fisher and Thilenius) correlated well with cast volume, with the corrected prism method of Fisher showing a best fit (r = 0.98, y = 1.1 + 0.9 x, standard error of the estimate = 3.6). Cast volumes calculated using our echocardiographic formula were then examined relative to the volumes derived from radiographic images of the RV casts. Volumes calculated using the corrected area-length Thilenius formula correlated best with those obtained using our derived 2-dimensional echocardiographic formula (r = 0.96, y = 4.6 + 1.0 x, standard error of the estimate = 6.8). These data confirm that volume calculated using the suggested optimal echocardiographic formula correlates well with volume obtained using derived angiographic data. Accordingly, confirmation in humans by the use of angiography is a rational step.

Left ventricular hamartoma associated with ventricular tachycardia

Cardiac hamartomas are a rare type of benign tumor affecting the heart. We describe a 33-year-old patient who presented with a wide complex tachycardia. Diagnostic imaging revealed a mass in the patients left ventricular wall, near the apex of the heart. The mass was surgically resected and appeared benign. Its pathology was that of a hamartoma of mature cardiac myocytes. Postoperative electrophysiology evaluation showed no inducible focus and the patient remains alive and asymptomatic after 2 years of follow-up.

Effect of hyperosmotic mannitol on magnetic resonance relaxation parameters in reperfused canine myocardial infarction

To determine how administration of a hyperosmotic agent alters regional nuclear magnetic resonance (NMR) relaxation parameters and imaging characteristics in ischemic-reperfused myocardium, 7 dogs were infused with mannitol for 15 minutes before and after the release of a 3 hour left anterior descending coronary artery (LAD) occlusion. Nine control animals received normal saline during the 3 hour occlusion and 1 hour reperfusion periods. Normal posterior left ventricular (LV) wall and the ischemic anterior LV wall (risk area) myocardium was sampled for calculation of segmental microsphere myocardial blood flow, % tissue water content, NMR relaxation times (T1, T2) and myocyte ultrastructure using electron microscopy. Mean infarct T1 values were 14% greater than normal segments in saline-treated controls, but only 5% greater after mannitol. The difference in tissue water content between infarcted and normal segments was 4% in saline-treated (83 vs. 79%) compared to 2% in mannitol-treated dogs (79 vs. 77%). T1, T2 and % water content of control infarct segments were greater than treated infarcts (p less than 0.01). T1 and T2 rose as occlusion flow fell below 0.5 ml/min/g in control hearts but did not rise until flows were reduced to 0.1 ml/min/g in mannitol-treated hearts. Areas of increased signal in T1 and T2 NMR images correlated well with histochemical infarct volume (r = 0.98, SEE = 1.1 cc) in mannitol-treated dogs, but infarct borders were qualitatively less well-defined than in controls. We concluded that mannitol (1) diminishes tissue edema and reduces NMR relaxation parameters (T1, T2) in infarcted myocardium; and (2) attenuates the rise in T1 and T2 and ultrastructural myocyte injury in ischemic-reperfused myocardium.

Local delivery of c‐myb antisense oligonucleotides during balloon angioplasty

Intraluminal delivery of antisense oligonucleotides to c-myb was assessed following balloon angioplasty in swine peripheral arteries. Successful delivery and intramural persistence of oligonucleotide for over 24 h were demonstrated following angioplasty with hydrogel balloons coated with 32P-labeled antisense. Delivery of fluorescein-labeled antisense demonstrated further localization within the arterial media and intracellularly. Preliminary in vitro studies demonstrated the feasibility of inhibition of porcine lymphocyte proliferation using the murine antisense to c-myb. Twelve iliac or carotid arteries underwent angioplasty with antisense-coated balloons, while the contralateral vessels underwent angioplasty with the same-sized balloons coated with the complementary sense strand. Six to seven days later, dilated arterial segments were surgically isolated. In 10 of 12 vessel pairs, antisense-treated vessels demonstrated less cellular proliferation than did contralateral sense-treated vessels, as assessed by quantitative immunohistochemical staining of proliferating cell nuclear antigen, and smooth muscle cell proliferation was reduced 18% in antisense-treated vessels compared to the contralateral sense-treated vessels (PCNA-positive nuclear area: 7.7 +/- 4.9% vs. 9.3 +/- 5.2%, P < 0.04)-intraluminal delivery of antisense oligonucleotides to c-myb is feasible with a catheter-based system and may reduce smooth muscle cell proliferation following arterial injury.

Comparison of contrast X-ray biplane cineangiography and technetium-99m radionuclide scans for measurement of ventricular volumes in human autopsy hearts

The area-length method is widely used in the determination of left ventricular volume. Although previous studies have reported that this technique overestimates true volume (TV), it is unknown whether this overestimation is the same at different volumes. In the present study, with the use of 10 postmortem human hearts, left ventricular volumes were determined by contrast x-ray biplane cine ventriculography (LVA), biplane radionuclide (LVR), and absolute-counts (LVC) technetium scans, and the results were correlated with TV. LVA correlated well with TV (r = 0.98). LVR correlated well with TV (r = 0.97), and LVR also correlated well with LVA (r = 0.96). Both area-length techniques (LVA and LVR) resulted in overestimation of TV with an upward shift of the regression line of 30.4ml +/- 3.8 (SEM) for LVA and 28.5 +/- 4.4 for LVR. The percentage of overestimation error was significantly greater at smaller left ventricular volumes (error = 33% at TV = 30ml and 10% at TV = 100ml, p less than 0.001). LVC correlated well with TV (r = 0.99), TVA, and LVR but underestimated TV. Thus left ventricular volumes can be reliably obtained from LVR and LVA by means of the area-length method and from LVC. When the area-length method is utilized, the percentage of error in the determination of left ventricular volume is proportional to 1/TV.

Linear Radiofrequency Microcatheter Ablation Guided by Phased Array Intracardiac Echocardiography Combined with Temperature Decay

Background: Fluoroscopy‐guided catheter placement is limited in its ability to determine electrode‐endocardial contact and involves radiation exposure. We hypothesized that (1) intracardiac echocardiography (ICE) would provide superior assessment of linear electrode contact compared to fluoroscopy and (2) slow temperature decay upon discontinuation of the radiofrequency current (time for temperature to fall 90% after a 10‐second test application of the radiofrequency current T90) would indicate optimal electrode‐myocardial contact.