Patrick Hall

Intracoronary Stenting Without Anticoagulation Accomplished With Intravascular Ultrasound Guidance

BACKGROUND The placement of stents in coronary arteries has been shown to reduce restenosis in comparison to balloon angioplasty. However, clinical use of intracoronary stents is impeded by the risk of subacute stent thrombosis and complications associated with the anticoagulant regimen. To reduce these complications, the hypothesis that systemic anticoagulation is not necessary when adequate stent expansion is achieved was prospectively evaluated on a consecutive series of patients who received intracoronary stents. METHODS AND RESULTS From March 1993 to January 1994, 359 patients underwent Palmaz-Schatz coronary stent insertion. After an initial successful angiographic result with < 20% stenosis by visual estimation had been achieved, intravascular ultrasound imaging was performed. Further balloon dilatation of the stent was guided by observation of the intravascular ultrasound images. All patients with adequate stent expansion confirmed by ultrasound were treated only with antiplatelet therapy (either ticlopidine for 1 month with short-term aspirin for 5 days or only aspirin) after the procedure. Clinical success (procedure success without early postprocedural events) at 2 months was achieved in 338 patients (94%). With an inflation pressure of 14.9 +/- 3.0 atm and a balloon-to-vessel ratio of 1.17 +/- 0.19, optimal stent expansion was achieved in 321 of the 334 patients (96%) who underwent intravascular ultrasound evaluation, with these patients receiving only antiplatelet therapy after the procedure. Despite the absence of anticoagulation, there were only two acute stent thromboses (0.6%) and one subacute stent thrombosis (0.3%) at 2-month clinical follow-up. Follow-up angiography at 3 to 6 months documented two additional occlusions (0.6%) at the stent site. At 6-month clinical follow-up, angiographically documented stent occlusion had occurred in 5 patients (1.6%). At 6-month clinical follow-up, there was a 5.7% incidence of myocardial infarction, a 6.4% rate of coronary bypass surgery, and a 1.9% incidence of death. Emergency intervention (emergency angioplasty or bailout stent) for a stent thrombosis event was performed in 3 patients (0.8%). The overall event rate was relatively high because of intraprocedural complications that occurred in 16 patients (4.5%). Intraprocedural complications, however, decreased to 1% when angiographically appropriately sized balloons were used for final stent dilations. There was one ischemic vascular complication that occurred at the time of the procedure and one ischemic vascular complication that occurred at the time of angiographic follow-up. By 6 months, repeat angioplasty for symptomatic restenosis was performed in 47 patients (13.1%). CONCLUSIONS The Palmaz-Schatz stent can be safely inserted in coronary arteries without subsequent anticoagulation provided that stent expansion is adequate and there are no other flow-limiting lesions present. The use of high-pressure final balloon dilatations and confirmation of adequate stent expansion by intravascular ultrasound provide assurance that anticoagulation therapy can be safely omitted. This technique significantly reduces hospital time and vascular complications and has a low stent thrombosis rate.

High pressure assisted coronary stent implantation accomplished without intravascular ultrasound guidance and subsequent anticoagulation

OBJECTIVES The purpose of this study was to determine the efficacy of treatment with antiplatelet therapy and no anticoagulation after high pressure assisted coronary stent implantation performed without intravascular ultrasound (IVUS) guidance. BACKGROUND Previous studies have shown that during IVUS-guided Palmaz-Schatz coronary stenting, it is safe to withhold anticoagulation when stent expansion has been optimized by high pressure balloon dilation. METHODS Patients that had successful coronary stenting without IVUS guidance were treated with ticlopidine, 500 mg/day, and aspirin, 325 mg/day, for 1 month and then received only aspirin, 325 mg/day, indefinitely. Patients were not treated with warfarin (Coumadin) or heparin after successful stenting. Clinical and angiographic events were assessed at 1 month. RESULTS A total of 201 intracoronary stents were implanted in 127 patients with 137 lesions. The average number of stents per lesion was 1.4 +/- 0.8, and the average number of stents per patient was 1.6 +/- 1.1. Stent deployment was performed for elective indications in 79% of procedures and for emergency indications in 21%. There were four stent thrombosis events for a per patient event rate of 3.1% and a per lesion event rate of 2.9%. CONCLUSIONS After high pressure assisted stenting performed without IVUS guidance, there was an acceptable incidence of 3.1% of stent thrombosis with the combination of short-term ticlopidine and aspirin therapy and no anticoagulation. Although the study involved only 127 patients, the results support the relative safety of stenting without IVUS guidance and with antiplatelet therapy only in comparison to historical trials on stenting performed with postprocedure anticoagulation.

Increased exercise capacity after digoxin administration in patients with heart failure

Failure to objectively assess the effect of digitalis on exercise capacity has resulted in controversy regarding its use in patients with chronic congestive heart failure. To clarify this situation, maximal treadmill testing with respiratory gas exchange analysis was performed on 11 patients (mean age 57 +/- 9 years) with chronic congestive heart failure with and without digoxin therapy. Ten of the 11 had a consistent third sound gallop, and the mean ejection fraction of the group was 24 +/- 10%. Rest heart rate was significantly higher (91 +/- 16 versus 102 +/- 16 beats/min; p less than 0.05) and rest systolic blood pressure was significantly reduced in the absence of digoxin (130 +/- 23 versus 121 +/- 15 mm Hg; p less than 0.05). No differences in heart rate or blood pressure were observed during exercise. Significant increases in ventilatory oxygen uptake were observed with digoxin submaximally (3.0 mph, 0% grade), at the gas exchange anaerobic threshold and at maximal exercise (mean increase of 2.6 ml/kg per min; p less than 0.02). An improvement in the estimated ratio of ventilatory dead space to tidal volume (VD/VT), an index of physiologic efficiency, occurred throughout exercise during digoxin therapy, and there was a significant negative correlation between the change in maximal oxygen uptake and change in maximal estimated VD/VT (r = -0.63; p less than 0.05). Thus, digoxin therapy is associated with a significant improvement in exercise capacity in patients with chronic heart failure, most likely due to an improved matching of ventilation to perfusion.

The signal averaged surface electrocardiogram and the identification of late potentials

V ENTRICULAR TACHYARRHYTHMIAS are a major cause of sudden cardiac death, especially in patients after myocardial infarction.‘** Accurate detection of those prone to malignant ventricular arrhythmias is essential to the prevention of sudden death. Many parameters, including clinical findings, and results from exercise testing, holter monitoring, and cardiac catheterization have been used to identify patients at high risk of sudden death.3-8 More recently, electrophysiologic stimulation testing in the cardiac catheterization laboratory has been used as a method of evaluating these patients.g*‘O The cost and invasive nature of this procedure, however, makes it impractical for use as a screening test for large numbers of patients. Tests designed to evaluate large populations at risk should be noninvasive, relatively inexpensive, and easily performed. The signal averaged electrocardiogram (ECG) may be such a screening test. This noninvasive, inexpensive procedure incorporates high gain amplification and signal averaging techniques to detect from ECG recordings on the body surface low amplitude, high frequency signals in or near the terminal portion of the QRS complex (Fig 1). There are many synonyms for these signals including delayed depolarization, arrhythmogenic ventricular activity (AVA), delayed wave-form activity (D wave), and ventricular late potentials (VLPs). These signals, called late potentials or LPs in this review (Fig 2) are rarely identified on routine ECG. Late potentials are thought to represent slow or delayed conduction through the myocardium. Within the last 10 years, numerous studies have provided convincing evidence that delayed conduction plays an important role in the genesis of ventricular arrhythmias.“-” Additional studies have corroborated the capacity of the highly amplified signal averaged ECG to detect such delayed activity.“-*’ Many investigators have used direct epicardial and endocardial mapping techniques to record delayed, fragmented electrical activity in patients and animals with ventricular arrhythmias.‘1-20,26-30 Several investigators have used both the body surface signal averaged ECG and endocardial catheter techniques to record delayed potentials in man and animals with ventricular tachyarrhythmias. They have found a close temporal correlation between the delayed potentials recorded by the two methods.‘g*20~30 While many studies lend theoretical support to the use of signal averaging techniques in identifying patients at risk of developing dangerous ventricular arrhythmias, the clinical role of this technique has not been defined. The intention of this review is to summarize the methodology and principles of signal averaged electrocardiography and to analyze critically many of the published reports to better define its current status.

Safety and efficacy of staple-mediated femoral arteriotomy closure: results from a randomized multicenter study.

Mechanical closure of percutaneous femoral arteriotomies following catheter based procedures remains problematic.

High-frequency electrocardiography: An evaluation of lead placement and measurements

Before there is widespread clinical application of the high-frequency ECG, differences resulting from the leads used and the measurement criteria for late potentials must be resolved. Therefore 113 consecutive patients without resting QRS conduction abnormalities referred for Holter monitoring were studied. Four different lead systems were used: a standard bipolar orthogonal lead system and three bipolar lead systems mapping the left ventricle. Measurements made of late potentials included normal and high-frequency QRS duration, their difference, the duration of low-amplitude signals (less than 40 uV) in the terminal QRS, and the root mean square of the last 40 msec of the high-frequency QRS duration. We found that the left ventricular leads tended to give more abnormal measurements than the orthogonal system and that the various measurements failed to agree with each other. In addition, even in this population in which abnormalities of QRS conduction were excluded, the late potential measurements tended to be more abnormal as QRS duration lengthened. These differences in lead systems and measurement criteria must be considered when clinically applying information regarding late potentials measured from the high-frequency ECG.

Clinical feasibility of 0.018-inch intravascular ultrasound imaging device

OBJECTIVES Intravascular ultrasound imaging (IVUS) is limited by the size of the imaging catheter. To facilitate imaging before and during interventions, a 30-MHz ultrasonic imaging device was developed that is the same dimension as a 0.018-inch guide wire. The purpose of this study was to evaluate the clinical feasibility of this device. METHODS AND RESULTS The imaging core was tested in 8 patients with the use of a monorail guiding sheath that was advanced through a 7F catheter. In addition, after coronary interventions, the standard guide wire was removed, the imaging core was placed inside a compatible balloon, and imaging was performed. In 4 patients, imaging was also performed with a standard 3.2F IVUS catheter. The lumen-plaque interface and the media-plaque interface were clearly visualized in all patients. There was no detectable loss in image quality between the new imaging device and the larger IVUS catheter, and measurements of lumen cross-sectional area were not statistically different. CONCLUSIONS Improvements in manufacturing technology have permitted the development of a mechanically rotating ultrasound imaging core 0.018 inches in diameter. It is compatible with current balloon catheters without degradation of image quality.

Implantation of the peripheral Wallstent for diffuse lesions in coronary arteries and vein grafts

The Wallstent (Schneider, Bulach, Switzerland) is available in different lengths without much compromise in flexibility and radial support compared to some other stents. We treated 24 patients (26 vessels) with diffuse coronary lesions or vein graft lesions with intravascular ultrasound-guided peripheral Wallstent implantation. Average balloon pressure during stent optimization was 16.4 +/- 2.7 atm. The stents could be successfully implanted in 24 vessels. Minimal lumen diameter and percent diameter stenosis after stenting were 3.60 +/- 0.62 mm and -8 +/- 13%, respectively. Average stent length was 63.7 +/- 22.7 mm. There was one procedure-related complication. After stenting, all patients were treated only with antiplatelet agents. During 1-month follow-up, there was one subacute stent thrombosis due to incomplete coverage of a distal dissection. These preliminary results show the feasibility of this novel approach in selected lesions.

Effects of altered cardiac ventricular chamber size on the electrocardiogram and position of the heart

It has been suggested that the electrocardiographic R-wave amplitude is related to the volume of blood in the left ventricle, the so-called Brody effect.le4 However, the evidence supporting this hypothesis is controversial, and the relation of the QRS complex to cardiac physiology has yet to be fully elucidated. Rather than by altering dipole formation, changes in ventricular volume may influence surface-recorded potentials indirectly by affecting cardiac position and orientation within the thorax.5 Other possible mechanisms include myocardial ischemia, left ventricular (LV) dyskinesis, changes in wall tension, altered conduction pathways and lung expansion.6y7 Determining the contribution of each of these factors to

853-4 The first use of medical simulation for the training of a new device roll-out

Background: Many factors have led to a decline in bedside cardiac examination skills which has been well documented at all levels of medical training and exacerbated by faculty who are themselves lacking in these skills. Methods: We have addressed two causative factors, the lack of exposure to “good teaching cases” and the dearth of experienced instruction, by the development of a multimedia database of audiovisual recordings of bedside cardiac examinations of over 200 patients with sounds, murmurs, and characteristic precordial and vascular pulsations. These “virtual patient examinations” (VPEs) are conducted by moving the stethoscope over the precordium while observing pulses, respiration, and/or postural maneuvers. VPEs include histories, casebased ECG, X-Ray, imaging, as well as instructional text and tutorials in which heart sounds and murmurs are related to dynamic images that explain causation. These programs have been used in medical school and teaching hospital curricula for over 8 years, and are designed for classroom, small group, self-study, and for testing of examination skills. This teaching software was evaluated in a controlled intervention study to assess whether multimedia-based instruction could improve examination skills in third-year medical students. For the intervention group, 22 students received 12 hours of supervised instruction with software and were compared with 18 students receiving no special instruction. Both groups were tested at the beginning and end of 8-week medical clerkships with a 50-question, interactive multimedia program that uses audiovisual recordings of actual patients. A subset of the intervention group was tested a year later to measure retention. Results: By paired t-test, mean test scores (out of 100) did not improve significantly for the control group (pretest: 62, posttest: 66, P = 0.3). Mean test scores for the intervention group improved from 58 to 74 (P = 0.00005). When 6 from the intervention group were tested a year later, their mean scores were 81 (P = 0.003). Conclusion: Complex cardiac examination skills can be taught and tested effectively and economically by VPE software, and these skills appear to be retained a year after training.