Combined physiologic and anatomic assessment of percutaneous revascularization using a Doppler guidewire and ultrasound catheter.

Previous investigations have established the utility of intravascular ultrasound (IVUS) examination for the evaluation of arterial dimensions and qualitative changes following percutaneous revascularization. More recently, the feasibility of obtaining intravascular physiology findings before and/or after percutaneous revascularization by use of an intravascular Doppler Flowire (Cardiometrics) has been demonstrated. Accordingly, we investigated the feasibility of using this combined physiologic/anatomic approach to evaluate individuals undergoing percutaneous revascularization of stenotic or occluded coronary and peripheral arteries. A total of 76 patients were evaluated using the Flowire to guide an IVUS catheter. Revascularization of coronary and peripheral vascular stenoses and/or occlusions was achieved in these patients by balloon angioplasty, directional atherectomy, excimer laser angioplasty, and thrombolytic therapy, alone or in combination. Physiologic findings obtained with the Flowire reinforced conclusions regarding morphologic severity of candidate stenoses and anatomic adequacy of revascularization following IVUS examination. In certain ambiguous cases, information gained by one modality clarified information obtained with the other. Finally, one modality may also serve as an alternative when logistics preclude the serial use of both. The preliminary experience obtained in this feasibility trial confirmed that IVUS and the Flowire may be combined to assess both candidate lesions as well as postprocedural patency in patients undergoing percutaneous revascularization. The combination of anatomic and physiologic data available from IVUS and Flowire provides a far more sensitive and possibly more accurate analysis of the adequacy of revascularization than has been possible by angiography alone. The extent to which such a detailed investigation is required to optimize interventional therapy on a routine basis is the subject of subsequent investigations.

Three-dimensional reconstruction of human coronary and peripheral arteries from images recorded during two-dimensional intravascular ultrasound examination.

BACKGROUND: Intravascular ultrasound provides high-resolution images of vascular lumen, plaque, and subjacent structures in the vessel wall; current instrumentation, however, limits the operator to viewing a single, tomographic, two-dimensional image at any one time. Comparative analysis of serial two-dimensional images requires repeated review of the video playback recorded during the two-dimensional examination, followed by a "mind's eye" type of imagined reconstruction. METHODS AND RESULTS: Computer-based, automated three-dimensional reconstruction was used to generate a tangible format with which to assess and compare a "stacked" series of two-dimensional images. Three-dimensional representations were prepared from sequential images obtained during intravascular ultrasound examination in 52 patients, 50 of whom were studied before and/or after percutaneous revascularization. Conventional two-dimensional ultrasound images were acquired by means of a systematic, timed pullback of the ultrasound catheter through the respective vascular segments. Images were then assembled in automated fashion to create a three-dimensional depiction of the vessel lumen and wall. Computer-enhanced three-dimensional reconstructions were generated in both sagittal and cylindrical formats. The sagittal format resulted in a longitudinal profile similar to that obtained during angiographic examination; in contrast to angiography, however, the sagittal reconstruction offered 360 degrees of limitless orthogonal views of the plaque and arterial wall as well as the vascular lumen. The cylindrical format yielded a composite view of a given vascular segment, and a hemisected version of the cylindrical reconstruction enabled en face inspection of the reconstructed luminal surface. Sagittal reconstructions facilitated analysis of dissections and plaque fractures resulting from percutaneous revascularization, and the hemisected cylindrical reconstructions enhanced analysis of endovascular prostheses. CONCLUSIONS: This preliminary experience demonstrates that computer-based three-dimensional reconstruction may further augment the use of intravascular ultrasound in assessing vascular pathology and guiding interventional therapy.

Clinical issues related to discontinuing digoxin therapy in elderly nursing home patients.

Digoxin is commonly used to treat congestive heart failure. Digoxin augments ventricular systolic performance, but does not benefit patients whose congestive heart failure is caused by poor diastolic function. We studied 47 elderly nursing home patients who were receiving long-term digoxin therapy. The left ventricular ejection fractions were measured using both a standard and a highly portable echocardiography machine. Thirty-five of 47 patients had normal ejection fractions (50% or greater). In this subgroup, 23 patients were in normal sinus rhythm. Digoxin was discontinued in 14 patients with good systolic function and normal sinus rhythm, but in nine cases physicians refused to stop the digoxin. Follow-up evaluations showed no deterioration off digoxin. Excellent correlations existed between estimated left ventricular ejection fractions from the two echocardiography machines. Many nursing home patients taking digoxin do not need it. Physician reluctance to discontinue digoxin may change with the availability of highly portable echocardiography.

Combination balloon-ultrasound imaging catheter for percutaneous transluminal angioplasty. Validation of imaging, analysis of recoil, and identification of plaque fracture.

BACKGROUND: We investigated the hypothesis that an ultrasound transducer positioned within an angioplasty balloon could be used to perform quantitative assessment of arterial dimensions before and after percutaneous transluminal angioplasty (PTA) and to identify certain mechanical alterations consequent to PTA, including vascular wall recoil and the initiation of plaque fractures. METHODS AND RESULTS: A combination balloon-ultrasound imaging catheter (BUIC) that houses a 20-MHz ultrasound transducer within and halfway between the proximal and distal ends of an angioplasty balloon was used to perform PTA in 10 patients with peripheral vascular disease. Each PTA site was also evaluated before and after PTA by standard (nonballoon) intravascular ultrasound (IVUS) technique. In eight patients in whom satisfactory images were recorded with the BUIC before PTA, luminal cross-sectional area (XSA) of stenotic sites (0.10 +/- 0.01 cm2) did not differ significantly from measurements of XSA by IVUS (0.09 +/- 0.01 cm2, p = NS). Likewise, minimum luminal diameter (Dmin) measured by BUIC (0.34 +/- 0.02 cm) was similar to that measured by IVUS (0.33 +/- 0.01 cm, p = NS). In nine patients in whom satisfactory images were recorded with the BUIC after PTA, XSA measured by BUIC (0.29 +/- 0.03 cm2) did not differ significantly from XSA measured by IVUS (0.30 +/- 0.03 cm2, p = NS). Dmin measured by BUIC after PTA (0.57 +/- 0.02 cm) was also similar to Dmin measured by IVUS (0.57 +/- 0.03 cm, p = NS). After PTA, XSA and Dmin measured immediately after deflation were significantly less than balloon XSA and diameter at full inflation, indicating significant elastic recoil of the dilated site. For the nine patients in whom post-PTA images were satisfactory for quantitative analysis, including four patients in whom recoil was 39%, 46%, 50%, and 61%, percent recoil measured 28.6 +/- 7.2%. Finally, plaque fractures were identified on-line in six of 10 patients (60%); in each case, initiation of plaque fracture was observed at inflation pressures of 2 atm or less. CONCLUSIONS: The results of this preliminary human investigation indicate that an ultrasound transducer positioned within an angioplasty balloon can be used to perform quantitative and qualitative analyses of lumen-plaque-wall alterations immediately preceding, during, and immediately after PTA in patients with peripheral vascular disease.

Catheter-based intravascular ultrasound discriminates bicuspid from tricuspid valves in adults with calcific aortic stenosis.

A catheter-based intravascular ultrasound transducer was used to study aortic valve morphology in adults with calcific aortic stenosis. Examination of 14 postmortem specimens disclosed that intravascular ultrasound consistently identified the number of cusps or the presence of a calcified median raphe in the conjoined cusp, or both, and thereby distinguished a calcified bicuspid from a calcified tricuspid aortic valve. These postmortem findings were then employed to identify valvular morphology in 15 patients undergoing diagnostic cardiac catheterization or balloon aortic valvuloplasty, or both. Reproduction of criteria established in vitro allowed discrimination of congenital valvular morphology in all 15 patients, including 7 in whom assessment by intravascular ultrasound was confirmed by subsequent pathologic examination. Identification of aortic valvular morphology by intravascular ultrasound has potential therapeutic implications for patients considered to be candidates for operative or nonoperative aortic valvuloplasty.

Percutaneous intravascular US as adjunct to catheter-based interventions: preliminary experience in patients with peripheral vascular disease.

Catheter-based ultrasound (US) transducers may be introduced into the vascular system to record high-resolution images of the vessel wall and lumen. The potential advantages and existing liabilities of percutaneous intravascular US as an adjunct to transluminal vascular recanalization were investigated. A 6.6-F braided, polyethylene catheter enclosing a rotary drive shaft with a single-element, 20-MHz transducer at the distal tip was used in 17 patients undergoing percutaneous transluminal (balloon) angioplasty (PTA) alone (10 patients), PTA with implantation of an endovascular stent (two patients), atherectomy alone (two patients), or laser angioplasty with PTA and/or atherectomy (three patients). The arteries treated and examined included the common iliac in five patients, the external iliac in two, the superficial femoral in nine, and a vein graft-arterial anastomosis in one. In 14 cases PTA was employed as sole or adjunctive therapy; plaque cracks were clearly delineated with intravascular US in all 14 (100%) and dissections were observed in 11 (78%). Plaque-arterial wall disruption was less prominent in the arteries treated with mechanical atherectomy. The results of laser angioplasty reflected the adjunctive modality employed. After stent implantation, serial intravascular US documented effacement of PTA-induced plaque cracks and/or dissections. Intravascular US also aided in the quantitative assessment of luminal cross-sectional areas after the procedures (19.0-51.8 mm2). The observations recorded in this preliminary group of 17 patients illustrate the potential utility of intravascular US as an adjunct to conventional angiography in patients undergoing percutaneous revascularization.

Clot-selective coronary thrombolysis with pro-urokinase.

Recognition that myocardial infarction is caused by coronary thrombosis has stimulated a search for a safe, rapidly acting, and effective thrombolytic regimen. Tissue plasminogen activator (t-PA) can provide relatively clot-selective thrombolysis, but one quarter of patients fail to achieve reperfusion, lysis speed is not optimal, and higher doses have been associated with an increased incidence of hemorrhagic stroke. We report the results of a multicenter study of pro-urokinase, a second naturally occurring plasminogen activator that has structural similarities to t-PA but has a different mechanism of action. Pro-urokinase was administered 3.9 +/- 1.1 hours after the onset of chest pain to 40 patients with acute myocardial infarction with angiographically confirmed complete coronary occlusion (TIMI grade 0). After a 90-minute intravenous infusion of pro-urokinase (4.7-9 million units, 36-69 mg) 51% (20 of 39) of the patients demonstrated reperfusion (TIMI grade 2 or 3) occurring 64.8 +/- 22.3 minutes after initiation of therapy. Fibrinogen levels fell only 10 +/- 17% from baseline, confirming the fibrin specificity of pro-urokinase. As with t-PA, however, this specificity was only relative. alpha 2-Antiplasmin decreased to 39% and plasminogen decreased to 64% of initial values. Fibrinogen degradation products increased 63% and the fibrin-specific D-dimer increased 8.7-fold. Thus, pro-urokinase produces relatively clot-selective coronary thrombolysis similar to that produced by t-PA, but the use of either pro-urokinase or t-PA alone in higher doses would be likely to produce more nonspecific effects.

Lipids, lipoproteins, fibrinogen and fibrinolytic activity in angiographically assessed coronary heart disease.

Plasma lipids, lipoproteins, fibrinogen and fibrinolytic activity (FA) were measured in 202 consecutive patients undergoing coronary angiography. Twenty-one patients, 13 men and 8 women with a mean age of 52.8 years and 56.7 years respectively, were found to be angiographically free of coronary artery disease (CAD) and served as the principal control group. Since this group contained a disproportionate number of subjects with risk factors such as family history, hypertension and smoking, a second control group of clinically healthy subjects selected for age was also tested. Their laboratory results were not used in the statistical calculations. The group with angiographic CAD consisted of 130 men (mean age 57.6 years) and 51 women (mean age 61.5 years). Abnormal angiograms were graded according to the number of major vessels with more than 50% stenosis involved. The laboratory variables which were significantly (p less than .01-.001) associated with the presence of CAD were: High density lipoprotein (HDL) when determined by polyacrylamide gel electrophoresis (PAGE) and expressed as a percentage of total lipoproteins rather than concentration, presence of Intermediate Density Lipoprotein (IDL), percent of Very Low Density Lipoprotein (VLDL), fibrinogen concentration and FA. The HDL2 subfraction was significantly inversely correlated only in women. The total plasma cholesterol was normal and virtually identical in both groups. Within the CAD group, only two of the laboratory results were significantly correlated with the extent of disease. By univariate analysis, the FA showed the closest association with the score for severity of CAD (p less than .001) followed by the presence of IDL (p less than .01). In conclusion, lipoprotein analysis by a method which measures not only HDL, but also LDL, VLDL and IDL, together with the determination of fibrinogen and FA provides information useful in the identification of individuals at risk for CAD.

Effect of local lidocaine anesthesia on ventricular escape intervals during permanent pacemaker implantation in patients with complete heart block.

Transient asystole is often noted during the course of permanent pacemaker implantation in patients with complete heart block. Since subcutaneous lidocaine is frequently used as the local anesthetic agent for permanent pacemaker implantation, the effect of this drug on ventricular escape intervals was studied. Ventricular escape intervals after transient cessation of pacing were studied in 9 patients with complete heart block before and 10, 30, and 45 minutes after subcutaneous lidocaine administration for permanent pacemaker implantation. The total lidocaine dose ranged from 170 to 400 mg (1.9 to 9.5 mg/kg of body weight). Therapeutic blood levels were achieved in 7 patients. The mean ventricular escape interval before lidocaine was 1.83 +/- 0.32 seconds, which increased to 2.58 +/- 1.35, 2.96 +/- 1.06, and 2.68 +/- 1.27 seconds at 10, 30, and 45 minutes after lidocaine (p less than 0.02). The mean maximal escape interval before lidocaine was 2.06 +/- 0.30 seconds, which increased to 3.80 +/- 1.44 seconds (p less than 0.01), a mean increase of 84%. The percent increase in maximal escape interval was related directly to the peak lidocaine level achieved. After lidocaine administration, 5 patients had asystole greater than 4 seconds and 1 required resumption of pacing. Thus, subcutaneous lidocaine contributes to the occurrence of asystole seen during permanent pacemaker implantation. It is advisable to limit the amount of lidocaine administered during permanent pacemaker implantation to the minimum necessary to achieve adequate local anesthesia. Strong consideration should be given to the use of a temporary pacemaker in patients with complete heart block during permanent pacemaker implantation even in the absence of previous asystole.

Transfemoral temporary pacing and deep vein thrombosis.

The incidence of deep vein thrombosis following transfemoral temporary pacing was prospectively assessed in 20 consecutive patients using serial 125I-fibrinogen scanning, impedance plethysmography, and measurements of fibrin degradation products. Four patients underwent venography. Of the twenty patients, five (25%) had definite evidence of deep vein thrombosis, six demonstrated equivocal abnormalities, and nine had no evidence of thrombosis. Thrombosis was found only in the legs used for pacing. Of the five with deep vein thrombosis, one had positive findings in all the noninvasive tests. Venography confirmed the diagnosis in the other four; one had thrombosis of the femoral vein, one had thrombosis of several calf veins, and one had thrombosis of both the thigh and calf veins; the fourth patient had thrombosis of the entire deep venous system of the leg. This latter patient was the only one who had clinical evidence of venous thrombosis. The patients with deep vein thrombosis did not differ in clinical characteristics from those without thrombosis. There was no relationship between the occurrence of deep vein thrombosis and the number of venepunctures, the state of the electrode, the presence of the introducer sheath in the femoral vein, or the duration of pacing. In conclusion, deep vein thrombosis is a common complication of transfemoral temporary pacing and the high incidence of its occurrence should be considered before deciding upon the site of entry for a temporary pacemaker.

Multilevel atrioventricular block.

Arrhythmias displaying conduction disturbances consistent with block at more than one level within the atrioventricular conduction system were seen in 36 patients during a two year period in a community hospital. Two levels of block were postulated in each patient; one patient also demonstrated a third level of block. In 24 patients (Type A), there was an integral conduction ratio at the upper level of block. This pattern was most frequently seen in atrial flutter (mean atrial rate 284 +/- 35 beats/min) with 2:1 block at the upper level and Wenckebach at the lower level. Progression to 2:1 block at the lower level resulted in 4:1 block. Twelve patients (Type B) had a nonintegral conduction ratio of their block at the upper level with a mean atrial rate of 162 +/- 62 beats/min. Their conduction patterns consisted of Wenckebach block at the upper level with either integral (2:1) or nonintegral (Wenckebach) block at the lower level. The presence of multilevel block was not related to specific etiological diagnoses, medications, or electrolyte patterns. It is suggested that multilevel block is a common, frequently transient, conduction pattern seen in a variety of clinical conditions. It is readily recognized from a standard electrocardiogram and, of itself, has no short-term detrimental prognostic implications.