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Biomedical subjects

H J Geschwind

Publications and source records attributed to H J Geschwind.

45 records · Page 3Linked to original sources
PubMed1987

Development and experimental application of contact probe catheter for laser angioplasty.

A sapphire contact probe laser catheter was developed to increase the dimensions of tunnels created by laser angioplasty. The device consisted of a round sapphire probe (2.2 mm diameter) attached to an 8F catheter into which a 0.2 mm optical fiber was inserted with a tip maintained at 3 mm from the sapphire. The fiber was connected to a continuous wave neodymium yttrium aluminum garnet (Nd-YAG) laser. A saline perfusate was circulated through the catheter during laser emissions to prevent excessive heating of the fiber tip. The system was used in vitro on 16 sections of atherosclerotic calcified human cadaver aortic walls, using diluted blood as a medium, at powers ranging from 10 to 40 W and exposure times from 1 to 4 seconds. Six craters were created at each energy level. The system was also used on six human cadaver, agar-embedded, obstructed iliac and femoral arteries, using 40 W and 2 second laser emissions. Dimensions of probe-created craters were compared with those obtained using bare fibers. The shape of the probe craters was that of a truncated cone with the entry hole wider than the exit, as opposed to the cylindrical shape created with unmodified bare fibers. At 120 J (seconds X watts), areas of entry and exit probe-formed holes were greater than those created with the bare fibers (6.7 +/- 0.5 and 3.4 +/- 0.6 versus 0.2 +/- 0.01 mm2, respectively, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1987

Efficiency and safety of optically modified fiber tips for laser angioplasty.

To evaluate the safety and efficiency of optically modified fiber tips, craters were created in human cadaver atherosclerotic arterial walls using sapphire contact probes and lensed fibers connected to a continuous wave neodymium yttrium aluminum garnet (Nd-YAG) laser. Laser energy was emitted at a constant level of 50 J. The sapphire contact probe catheter consisted of a round 2.2 mm diameter synthetic sapphire attached to an 8F catheter into which a 0.2 mm diameter optical fiber was inserted with the distal tip maintained at 3 mm from the sapphire. The lensed fiber catheter consisted of a 0.2 mm optical fiber at the end of which a 1 mm diameter lens was made. The fiber was inserted into a 5F low profile balloon catheter with the lens maintained 3 mm beyond the catheter tip. During laser emissions the catheter tips were maintained in a stationary position in contact with tissue targets immersed in blood at an angle of 90 degrees. The diameter of holes at the entry and exit of craters, the depth of craters and thermal injury to adjacent tissue (rim of carbonization and vacuolization) were measured with microscopy. The volume of tissue removed was derived from these values. Controlled effect index was determined as the ratio of diameter of holes and the extent of thermal injury. Efficiency was determined as the ratio of volume of tissue removed and the energy required to vaporize tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1986

Laser angioplasty of arterial stenoses.

To establish the optimal conditions for recanalization of obstructed arteries without damage to vessel walls, an Nd-YAG laser coupled to a 0.2-mm-diameter optical fiber was used on obstructed human cadaver coronary and peripheral arteries and on popliteal arteries in amputated limbs. Vaporization of atheromatous plaques was consistently obtained with energy of 360-600 J and a diluted blood perfusate (3 g/100 ml hemoglobin) at a rate of 30 ml/min. The arterial wall was protected from thermal injury by inserting the optical fiber into an inflated balloon catheter and by cooling the system with the perfusate. Since recanalization of occluded arteries was consistently obtained without damage to the arterial wall or debris and thin and flexible optical fibers were easy to guide in the arteries, percutaneous transluminal Nd-YAG laser angioplasty was used in obstructed femoral and popliteal arteries in 12 patients. The first trials in man with Nd-YAG laser showed the method to be feasible, effective, and at low risk, although further studies are required to improve penetration of the obstruction and increase the diameter tunnel.

Angioplasty, Balloon↗
PubMed1984

Sympathetic nervous system activation in postextrasystolic potentiation: role of catecholamine release in enhancement of ventricular function.

The role of catecholamines in postextrasystolic potentiation was assessed in 30 patients during continuous coupled right ventricular pacing. Hemodynamic data were recorded in 15 patients (group 1); in the other 15 patients (group 2), coronary blood flow and metabolic variables, including catecholamines, were measured. Data were recorded in the control state and after 10 minutes of coupled pacing. Both groups had similar control pulse rates and mean aortic pressures: these variables decreased abruptly by 32 beats/min and 12 mm Hg, respectively, (p less than 0.001 for each) after the initiation of coupled pacing. In group 1, all indexes of left ventricular function and contractility increased during coupled pacing (p less than 0.001 for each), thus confirming postextrasystolic potentiation. In group 2, coupled pacing increased coronary blood flow, myocardial oxygen consumption and free fatty acid uptake (p less than 0.001 for each) but not lactate extraction. Plasma epinephrine was unchanged, but norepinephrine levels increased in arterial (421 +/- 27 to 576 +/- 41 ng/liter) and coronary sinus plasma (611 +/- 46 to 836 +/- 46 ng/liter) (p less than 0.001 for both). Indirectly calculated norepinephrine release within the myocardium increased from 25.6 +/- 2.8 to 39.7 +/- 5.2 ng/min (SEM) (p less than 0.05), suggesting a sympathetic nervous system activation. It is argued that coupled pacing acutely lowered mean aortic pressure, leading to baroreflex sympathetic activation which may contribute to augmented cardiac contractility in postextrasystolic potentiation.

Adolescent↗
PubMed1984

Conditions for effective Nd-YAG laser angioplasty.

To establish the optimal conditions for recanalisation of obstructed arteries without damage to vessel walls, a Nd-YAG laser coupled to a 0.2 mm diameter optic fibre was used on obstructed human cadaver coronary and peripheral arteries and on popliteal arteries in amputated limbs. Vaporization of atheromatous plaques was consistently obtained with an energy of 360-600 J and a diluted blood perfusate (3 g/100 ml haemoglobin) at a rate of 20 ml/min. The arterial wall was protected from thermal injury by inserting the optic fibre into an inflated balloon catheter and by cooling the system with the perfusate. Since recanalisation of occluded arteries was consistently obtained without damage to the arterial wall or debris and thin and flexible optic fibres were easy to guide in the arteries, percutaneous transluminal Nd-YAG laser angioplasty was used in obstructed femoral and popliteal arteries in three patients. The first European trials in man showed the method to be feasible, effective, and harmless, although further studies are required to improve penetration of the obstruction and increase the diameter of tunnel.

Angioplasty, Balloon↗