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Biomedical subjects

J M Isner

Publications and source records attributed to J M Isner.

At least 289 records · Page 16Linked to original sources
PubMed1986

Relative contribution of inotropic and vasodilator effects to amrinone-induced hemodynamic improvement in congestive heart failure.

The relative contribution of inotropic and vasodilator effect to amrinone-induced hemodynamic improvement in congestive heart failure (CHF) is unknown. In 9 patients with CHF, the effects of amrinone and nitroprusside on hemodynamic and radionuclide measurements were compared to determine whether reduced afterload accounts for the amrinone-induced decrease in left ventricular end-systolic volume. In each patient, the end-systolic pressure-volume relation was derived using nitroprusside. After terminating nitroprusside treatment, intravenous amrinone (3 mg/kg) caused end-systolic volume to decrease from 148 +/- 32 ml/m2 (mean +/- standard deviation) to 133 +/- 32 ml/m2 (p less than 0.05), causing an increase in cardiac index from 1.9 +/- 0.8 to 2.7 +/- 0.8 liters/min/m2 (p less than 0.001). Arterial end-systolic pressure decreased in all patients during amrinone administration, from 96 +/- 22 to 84 +/- 19 mm Hg (p less than 0.005), as did systemic vascular resistance. Nitroprusside doses needed to match the decrease in LV end-systolic volume induced by amrinone caused significantly greater decreases in arterial end-systolic pressure than did amrinone (p less than 0.01). The amrinone-induced decrease in end-systolic volume exceeded that predicted for a pure vasodilator based on arterial end-systolic pressure and the nitroprusside-derived pressure-volume relation in 6 patients. In 3 patients, the decrease in end-systolic volume did not exceed that expected for a pure vasodilator. In conclusion, after amrinone treatment, afterload reduction occurs in all patients with severe CHF and is the sole effect in some.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Comparison of the electrocardiographic and hemodynamic responses to ionic and nonionic radiocontrast media during left ventriculography: a randomized double-blind study.

The ECG and hemodynamic responses to a standard ionic radiographic contrast agent (diatrizoate) were measured and compared to those induced by iopamidol, a newly developed nonionic agent, during left ventriculography. Studies were performed using randomized double-blind techniques in 46 patients with suspected coronary artery disease who were scheduled for cardiac catheterization. A nuclear probe was used to measure left ventricular ejection fraction and relative ventricular volume before and immediately after left ventriculography. Bolus injections of diatrizoate and iopamidol induced similar significant decreases in left ventricular end-diastolic and end-systolic volume and similar significant increases in both left ventricular end-diastolic pressure (p less than 0.05) and systolic ejection fraction (p less than 0.01 vs baseline). Both agents induced modest increases in heart rate, but only the increase induced by diatrizoate was significant (p less than 0.01). The maximal rate of left ventricular pressure rise was not significantly altered by either agent. Iopamidol induced a slight increase in QRS duration (p less than 0.05); neither agent effected a significant change in QT duration. We conclude that the hemodynamic effects during left ventriculography using diatrizoate and iopamidol are similar. These findings do not justify the large-scale substitution of more expensive nonionic radiographic contrast agents for standard ionic agents such as diatrizoate in left ventriculography.

Cardiac Catheterization↗
PubMed1986

Comparison of histamine release effects of ionic and non-ionic radiographic contrast media.

Histamine release may underline the side effects (particularly anaphylactoid) of radiographic contrast media. To study the histamine-releasing properties of radiographic contrast media, this study measured the in vitro release of histamine from human basophils incubated with diatrizoate, a standard ionic radiographic contrast agent, and with iopamidol, a newly developed non-ionic contrast agent. The basophils were separated from blood obtained from 16 patients scheduled for coronary angiography. For both diatrizoate and iopamidol, the concentration of histamine released varied as the concentration of radiographic contrast agent was increased from 0.075 M to 0.50 M. At the higher concentrations tested, the percent of histamine released by iopamidol was about half that released by diatrizoate (p less than 0.05). These data suggest that the use of non-ionic contrast media may involve less patient risk from the histamine-mediated allergic and/or hemodynamic side effects associated with radiographic contrast procedures.

Diatrizoate↗
PubMed1986

Use of pulsed energy delivery to minimize tissue injury resulting from carbon dioxide laser irradiation of cardiovascular tissues.

The carbon dioxide (CO2) laser has been utilized for preliminary intraoperative cardiovascular applications, including coronary endarterectomy and ventricular endocardiectomy. CO2 lasers used for these applications have been operated in the continuous wave, chopped or pulsed mode at low peak powers. To evaluate the extent of boundary tissue injury, continuous, chopped and pulsed energy delivery of CO2 laser emission was used to bore through 192 5 mm thick myocardial slices in air. Continuous, chopped and pulsed delivery at a peak power of 500 W or less failed to eliminate light microscopic or ultrastructural signs of thermal injury. Only when a high energy CO2 laser (pulse energy 80 to 300 mJ, pulse duration 1 microseconds) was used at a peak power greater than 80 kW were all signs of thermal injury eliminated; furthermore, high peak power prevented thermal injury only when the beam was focused to achieve a peak power density greater than 60 kW/mm2. Under these conditions, pathologic findings were identical to those observed using excimer wavelengths. The results of these experiments indicate that: conventional CO2 lasers fail to minimize boundary tissue injury, elimination of thermal injury during intraoperative laser ablation requires that CO2 laser energy be focused to achieve a peak power density greater than 60 kW/mm2, and elimination of thermal injury can be achieved at a variety of wavelengths, provided that an appropriate energy profile is employed.

Carbon Dioxide↗
PubMed1985

Reduction of laser-induced pathologic tissue injury using pulsed energy delivery.

Continuous-wave (CW) laser irradiation of cardiovascular tissues is characterized by 2 distinctive histologic findings: a superficial zone of coagulation necrosis and a subjacent zone of polymorphous lacunae. The present investigation was designed to determine whether such injury could be eliminated by altering the temporal profile of laser energy delivery. One hundred forty-five myocardial slices were irradiated with an air-tissue interface using CW laser irradiation at wavelengths of 488 to 515 nm (argon), 1,064 nm (Nd-YAG) and 10,600 nm (CO2). Pulsed laser irradiation included 248 nm (excimer); 355, 532 and 1,064 nm (Nd-YAG); and 515 nm (mode-locked argon). Energy profiles in the pulsed mode included a range of repetition rates (1 Hz to 256 MHz), pulse duration (0.2 to 358 ns) and pulse energies (2 nJ to 370 mJ). Resultant average powers were 0.1 to 38 W. Grossly visible charring of myocardial tissue was observed at all laser wavelengths when the laser energy profile was CW or pulsed at high repetition rates (more than 2 KHz) and low pulse energies (less than 3 mJ) independent of the wavelengths used. In contrast, when laser energy was pulsed at low repetition rates (less than 200 Hz) and large pulse energies (more than 10 mJ), neither gross nor histologic signs of thermal injury were observed. Pathologic injury associated with laser-induced tissue ablation may thus be substantially reduced by use of pulsed energy delivery at low repetition rates. Potential advantages of pulsed laser energy include a more benign healing process, a less thrombogenic surface, and improved preservation of structural tissue integrity.

Animals↗
PubMed1985

Identification of photoproducts liberated by in vitro argon laser irradiation of atherosclerotic plaque, calcified cardiac valves and myocardium.

To determine how laser light effects alterations in cardiovascular tissue, photoproducts liberated as the result of argon laser irradiation of atherosclerotic plaque, myocardium and calcified aortic valve leaflets were analyzed by gas chromatography, gas chromatography-mass spectrometry and absorbance spectroscopy. The products formed in gas phase are those expected when proteins and porphyrins are pyrolyzed--light hydrocarbon fragments, carbon monoxide and water vapor. The laser-generated products dissolved in solution are those expected when a protein chain or porphyrin ring is degraded in a thermal reaction, namely protein fragments and nitrogen heterocyclic ring fragments. These photoproducts are those typical of combustion or thermal degradation, and indicate that the fundamental nature of laser irradiation of coronary plaque, myocardium and calcified valve leaflets is thermal rather than photochemical. Thermal degradation of myocardium is more extensive than thermal degradation of atherosclerotic arteries or calcified valves because the red hue of myoglobin-containing myocardium enhances the absorption of the blue-green argon laser light. In contrast, the yellow-white hue of both atherosclerotic plaque and calcified aortic valve leaflets allows less complete absorbance of the argon laser light, leading to a lesser amount of converted heat and, therefore, less complete thermal degradation.

Arteriosclerosis↗
PubMed1985

Congenital pericardial defect diagnosed by computed tomography.

Complete or partial absence of the pericardium is a relatively rare disorder. While physical examination, electrocardiogram, and chest x-ray may suggest the diagnosis, definitive noninvasive diagnosis has until recently not been possible. In the patient described in the present report, the basis for chest pain initially attributed to myocardial ischemia was established noninvasively by computed tomographic examination of the chest to be congenital absence of the left pericardium. Experience with this patient emphasizes the fact that one of the known bases for nonischemic chest pain--congenital pericardial defects--can be precisely defined by contrast-negative computed tomographic imaging.

Adult↗
PubMed1985

Laser-assisted debridement of aortic valve calcium.

Experimental debridement of aortic valve calcium by means of laser phototherapy was investigated in vitro. Near-total debridement of calcific deposits observed on pretreatment x-ray films was accomplished using carbon-dioxide laser phototherapy. Analysis of liberated photoproducts suggests that debridement is effected by thermal degradation of the surrounding connective tissue envelope and thermal expansion of the calcific nodules. These results suggest that in selected patients with calcific aortic stenosis, it may be possible to perform intraoperative laser-assisted debridement of aortic valve calcium in order to preserve the native aortic valve and thus avoid prosthetic valve replacement.

Aged↗
PubMed1985

Limb loss due to transvenous endocardial pacemaker therapy.

Although intravenous thrombosis frequently complicates placement of transvenous endocardial leads in patients with permanent pacemakers, clinical manifestations of upper extremity thrombosis are uncommon. Most, including upper extremity edema, cervical venous engorgement, and even superior vena cava syndrome, can be successfully managed with conservative therapy. In the patient described in the present report, clinical manifestations of pacemaker-electrode thrombosis were neither mild nor responsive to conservative therapies: in this patient, pacemaker-electrode thrombosis ultimately required amputation of the right upper extremity. Complications of the magnitude described in this patient emphasize the need for continual review of the indications for pacemaker therapy as understanding of the risk-benefit ratio of this procedure broadens.

Aged↗
PubMed1985

Laser photoablation of pathological endocardium: in vitro findings suggesting a new approach to the surgical treatment of refractory arrhythmias and restrictive cardiomyopathy.

In selected patients, malignant ventricular tachyarrhythmias have been successfully abolished by excision of subendocardial arrhythmogenic foci. Likewise, in certain patients in whom restrictive cardiomyopathy is due to endocardial thickening, endocardial resection has resulted in hemodynamic improvement. The present study was designed to explore the utility, in vitro, of laser photoablation of pathologically thickened endocardium. Endocardial photoablation was easily accomplished regardless of etiological or anatomical variations using either the focused beam of a carbon dioxide laser or argon laser light delivered through a 200-microns optical fiber. Photoablation of areas as large as 3.9 X 1.3 cm was performed within 40 seconds. The extent or depth of endocardial photoablation could be limited to 2 mm2 in area or 1 mm in depth using either form of laser therapy. These in vitro results suggest that either carbon dioxide or argon laser phototherapy can be successfully applied to the surgical treatment of refractory arrhythmias and restrictive cardiomyopathy. Advantages of laser photoablation include speed and precision. Furthermore, laser photoablation obviates the difficulty associated with conventional techniques in establishing tissue planes.

Argon↗
PubMed1985

The excimer laser: gross, light microscopic and ultrastructural analysis of potential advantages for use in laser therapy of cardiovascular disease.

Excimer lasers are pulsed gas lasers that use a mixture of a rare gas and halogen as the active medium to generate pulses of short wavelength, high energy ultraviolet light. A krypton-fluoride gas mixture was used to achieve an excimer emission at a wavelength of 248 nm. A total of 30 atherosclerotic coronary artery segments were irradiated over a range of pulse energies (250 to 750 mJ), repetition rates (2 to 25 Hz), average powers (1.9 to 18.8 watts) and cumulative exposures (3 to 12 seconds). In no case was there gross, light microscopic or ultrastructural evidence of the pathologic injury typically associated with continuous wave laser irradiation of coronary artery segments. Similar results were achieved after excimer laser irradiation of 30 samples of myocardium. Excimer irradiation of calcified aortic valve leaflets accomplished focal debridement without pathologic tissue injury; when total debridement was attempted, however, gross charring was observed. The paucity of pathologic alterations observed after excimer irradiation of cardiovascular tissue may prove beneficial in precisely controlling laser ablation of pathologic tissue without injury to the surrounding normal tissue. Clinical application of excimer laser irradiation requires resolution of several issues, including the development of suitable fiber optics and laser coupling, evaluation of potential ultraviolet toxicity, and demonstration that ultraviolet light can be transmitted through a blood-filled system.

Coronary Disease↗
PubMed1985

Comparison of left and right ventricular end-systolic pressure-volume relations in congestive heart failure.

A hemodynamic-radionuclide study was performed to compare the relations between end-systolic pressure and volume in the left and right ventricles in 10 patients with biventricular failure, and to correlate the end-systolic pressure-volume slope with baseline variables of systolic function. During nitroprusside or nitroglycerin infusion, or a combination of both, linear relations were found between end-systolic pressure and volume for both ventricles. In 9 of 10 patients, the end-systolic pressure-volume slope was greater for the left ventricle (mean +/- SD 1.12 +/- 0.36 mm Hg X m2/ml) than for the right ventricle (0.46 +/- 0.27 mm Hg X m2/ml) (p less than 0.001). In all 10 patients, the volume-axis intercept of the pressure-volume relation was greater for the left ventricle (82 +/- 66 ml/m2) than for the right ventricle (2 +/- 30 ml/m2) (p less than 0.005). Right ventricular pressure-volume slope correlated weakly with baseline right ventricular ejection fraction (r = 0.69, p less than 0.05), strongly with the baseline right ventricular end-systolic pressure-volume ratio (r = 0.89) and inversely with baseline right ventricular end-systolic volume (r = -0.86). In conclusion, 1) in patients with severe biventricular failure, changes in systolic pressure influence end-systolic volume more strongly in the right than in the left ventricle. 2) For the right ventricle, the slope of the end-systolic pressure-volume relation is directly related to rest indexes of systolic function. 3) The greater the end-systolic volume at rest, the greater the predicted improvement in right ventricular emptying for any vasodilator-induced reduction in pulmonary artery end-systolic pressure.

Adult↗
PubMed1985

Anorexia nervosa and sudden death.

Necropsy findings and electrocardiograms from three women with anorexia nervosa were reviewed. Necropsy examination failed to establish an anatomic cause of death. Electrocardiograms recorded days or less before death showed various degrees of Q-T interval prolongation: Q-T intervals corrected for heart rate measured 0.61 s, 0.47 s, and 0.46 s, respectively. Terminal ventricular tachyarrhythmias were documented in two patients, including torsade de pointes in one. The necropsy and clinical findings in these three cases provide evidence that sudden death in anorexia nervosa, like sudden death in liquid-protein dieting, may result from ventricular tachyarrhythmias related to Q-T interval prolongation. For such patients, electrocardiographic monitoring should be routine.

Adult↗
PubMed1985

Factors contributing to perforations resulting from laser coronary angioplasty: observations in an intact human postmortem preparation of intraoperative laser coronary angioplasty.

This investigation was designed to assess the potential use of laser coronary angioplasty as an intraoperative adjunct in the surgical treatment of ischemic heart disease. Among 17 postmortem hearts, simulated laser coronary angioplasty was performed at 53 sites with a No. 4F guiding catheter and 240 micron (200 micron core) quartz optical fiber. Perforation complicated laser coronary angioplasty in 33 (62%) of the 53 attempts. Most (n = 29) perforations were thermal; four were purely mechanical. Perforation sites were characterized by extensive calcific deposits (21 of 33 cases [64%] ) and the origin of a side branch (13 of 33 [39%] ). Excessive tortuosity of the extramural coronary artery contributed to arterial perforation in four cases, and precluded attempts to perform laser coronary angioplasty in two other cases. In 19 of the 53 attempts to perform laser coronary angioplasty, a high-frequency two-dimensional echocardiographic probe was used to image the coronary artery during antegrade manipulation of the optical fiber/guiding catheter and laser irradiation of the target arterial stenosis. Although perforation nevertheless occurred in 11 (58%) of 19 sites, only one mechanical perforation resulted; the remaining 10 were thermal. Characteristics of the perforation sites in this group were similar to those noted for the group as a whole. Experience with this model of laser coronary angioplasty indicates that even when access problems associated with percutaneous laser coronary angioplasty are obviated by a simulated intraoperative approach, perforation of the underlying coronary arterial wall continues to represent the "rate-limiting" complication of laser coronary angioplasty. Most perforations occurred in relation to calcific deposits, branch points, and tortuous coronary segments.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Factitious lowering of the serum potassium level after cardiopulmonary resuscitation. Implications for evaluating the arrhythmogenicity of hypokalemia in acute myocardial infarction.

Hypokalemia has been suggested as a predisposing factor to the development of fatal arrhythmias in acute myocardial infarction. Evidence cited to support this concept has been derived largely from studies in which the determination of the serum potassium level was made following a cardiac arrhythmia and/or arrest, and often following cardiopulmonary resuscitation (CPR); this postresuscitation potassium level has been considered to be representative of the prearrest value. In the patient described herein, serial determinations of serum potassium obtained fortuitously before and intentionally following sudden unexpected cardiac arrest in a hospitalized patient demonstrate that the prearrest serum potassium level cannot be inferred from electrolyte values obtained after CPR.

Acute Disease↗