Topical cardiac hypothermia for myocardial preservation.

We compared moderate (29 degrees C.) and profound (5 degrees C.) (ice chips) cardiac hypothermia for myocardial preservation during aortic cross-clamping for 30 or 60 minutes in a canine right heart bypass preparation. Ventricular function deteriorated significantly at 29 degrees C. but not at 5 degrees C. Maximum dp/dt declined only after 60 minutes of ischemia at 29 degrees C., and Vmax decreased after one hour at either temperature. Lactate and pyruvate washout were greater after 29 degrees C., and pyruvate production persisted after 60 minutes of ischemia at 29 degrees C. Reactive hyperemia was greater after 30 minutes of ischemia at 29 degrees C. Reactive hyperemia was greater after 30 minutes of ischemia at 29 degrees C., and total coronary flow remained elevated after 60 minutes of ischemia at 29 degrees C. Coronary flow distribution was not altered by hypothermia. Ultrastructural changes were primarily time dependent and not temperature dependent. Ice-induced subepicardial injury was not evident in the ultrastructure or by flow distribution. Sixty minutes of profound topical cardiac hypothermia is moderately well tolerated by the canine heart, but functional and structural alterations are evident.

Cold-blood potassium cardioplegia: evaluation of glutathione and postischemic cardioplegia.

Potassium (34 mEq/L) cardioplegia was induced with cold blood (CBK) in three groups of six dogs undergoing 60 minutes of myocardial ischemia at a systemic temperature of 27 degrees +/- 2 degrees and a myocardial temperature of 7 degrees +/- 2 degrees C (crushed ice). Group 1 (CBK) animals were reperfused initially with 400 ml cold blood over 8 to 10 minutes at increasing pressures of up to 75 mm Hg. Group II (CBK-K) dogs were reperfused in the same manner as Group I with the addition of potassium chloride, 30 mEq/L. In Group III (CBKG-KG) glutathione, 30 mg/100 ml, was added to both the pre- and postischemic perfusions with CBK. After 30 minutes of reperfusion control studies were repeated. Heart rate, peak systolic pressure, rate of rise of left ventricular pressure, maximum velocity of contractile element, pressure-volume curves, coronary flow distribution, muscle stiffness, and heart water were not significantly different from control values. Total coronary flow and myocardial uptake of oxygen, lactate, and pyruvate did not serve to separate the three groups; the same was true for right ventricular creatine phosphate, adenosine triphosphate, and adenosine diphosphate during ischemia and recovery. Ultrastructural myofibrillar lesions were noted in all groups. thus, postischemic cardioplegia and use of a physiological reducing agent do not enhance CBK cardioplegia with topical and systemic hypothermia.

Myocardial protection by intermittent perfusion with cardioplegic solution versus intermittent coronary perfusion with cold blood.

The myocardial protection provided by cardioplegic solution using buffered, isosmotic potassium (30 mEq. per liter) was compared with intermittent cold coronary perfusion for 2 hours of aortic cross-clamping in dogs. The cardioplegic solution (Group CS) or cold blood (Group CB) was infused every 15 minutes through a cooling coil to reduce the perfusate temperature to 5 degrees C. Myocardial function after 30 minutes of reperfusion and rewarming was reduced in Group CB with a significant reduction in peak systolic pressure at a left ventricular (LV) balloon volume of 20 ml. and a significant reduction of dp/dt. In contrast, in Group CS, LV function was unchanged from the base-line period. LV compliance also was significantly reduced in Group CB while being unchanged in Group CS. Myocardial extravascular water content, obtained by dessication, was significantly higher in Group CB than in Group CS, which may explain the reduction in compliance. Electron microscopy showed normal ultrastructure in Group CS but extracellular edema in Group CB. Total coronary blood flow showed a sustained increase during reperfusion in both groups. Oxygen consumption rose with rewarming to base-line levels in both groups, whereas lactate and pyruvate consumption was reduced in both groups, particularly Group CB. Cardioplegic solution thus appears to be superior to the intermittent perfusion of cold blood for myocardial protection. The addition of potassium arrest, by markedly reducing myocardial metabolism, improves the protection afforded by cold blood perfusion alone.

Topical cardiac hypothermia and phrenic nerve injury.

The relationship between ice-chip cardioplegia and impaired left diaphragmatic function was evaluated in dogs. Direct or indirect contact of the phrenic nerve with crushed ice for 30 or 60 minutes resulted in phrenic paralysis for 6 to 28 days, with responsiveness returning from 7 to 62 days later. Microscopical examination of injured nerves revealed injury to the myelin sheath and preservation of axons. Paralysis of the left diaphragm after topical cardiac hypothermia may be secondary to cold injury of the phrenic nerve, which is reversible.

Cold blood-diltiazem cardioplegia.

The calcium channel blocker, diltiazem, has been studied in the same model used for evaluation of cold blood-potassium cardioplegia. Six dogs (Group 1) had one hour of myocardial ischemia with topical ice (myocardial temperature, 7 degrees +/- 2 degrees C) after coronary perfusion with 200 ml of cold blood (5 degrees +/- 1 degree C) containing diltiazem, 400 micrograms per kilogram of body weight. Seven dogs (Group 2) had two hours of ischemia after perfusion with 200 ml of cold blood containing 200 micrograms/kg and reperfusion every 30 minutes with 100 ml of cold blood and diltiazem, 100 micrograms/kg. Baseline studies were repeated after rewarming and 40 minutes of reperfusion. No inotropic agents or calcium were used. Heart rate, peak systolic pressure, velocity of the contractile element, peak + rate of rise of left ventricular pressure (dP/dt), peak - dP/dt, dP/dt over common peak isovolumic pressure, left ventricular compliance and stiffness, and heart water were unchanged in Group 1. In Group 2, heart rate slowed (p less than 0.025) and compliance decreased (p less than 0.02). In both groups, coronary vascular resistance declined (p less than 0.001) and recovery of adenosine triphosphate (p less than 0.001), adenosine diphosphate (p less than 0.025), and the adenosine pool (p less than 0.001) was impaired. Ultrastructure was well preserved, but myofibrillar lesions were noted in Group 2. Diltiazem cardioplegia was associated with good functional recovery, but there was impairment of high-energy phosphate metabolism.

Topical cardiac hypothermia: the effect of methylprednisolone sodium succinate.

We evaluated the effects of methylprednisolone sodium succinate (MPSS) on 60 minutes of myocardial ischemia during profound (5 degrees C) topical cardiac hypothermia (ice chips) in a canine right heart bypass preparation. The ventricular function curve shifted to the right and downward, but not significantly, after ischemia, and stroke work declined significantly for both control and treated dogs. Contractility (rate of rise of left ventricular pressure and maximum velocity of the contractile element) declined for both groups but not significantly. Total coronary flow, oxygen consumption, and metabolism of lactate and pyruvate were not different for control and treated dogs. Ultrastructure of the outer and inner myocardium did not demonstrate benefit from MPSS. Intracellular and extracellular edema of moderate severity was slightly worse in the subendocardium, and reversible mitochondrial injury of a mild to moderate degreee was symmetrically present. Ice-related injury was not noted. We were unable to deomonstrate that pretreatment with MPSS favorably alters cardiodynamics or ultrastructure after 60 minutes of profound topical cardiac hypothermia.

Coronary venous arterialization: acute hemodynamic, metabolic, and chronic anatomical observations.

Nine dogs that had anastomosis of the internal mammary artery (IMA) to the left anterior descending coronary vein (LADV) were studied acutely on right-heart bypass. Occlusion of the left anterior descending coronary artery (LADA) and LADV without venous arterialization resulted in a significant decline in stroke work, total coronary flow, and myocardial oxygen uptake; with reactive hyperemia an increase in lactate and pyruvate consumption resulted. Occlusion of the LADA and LADV with VA did not change these variables greatly, except for a marked increase in total coronary flow with reactive hyperemia. Chronic venous arterialization in 14 dogs was associated with a 14% mortality, while 10 controls had a 40% mortality. Dogs were killed at six weeks, and prior angiography in 9 showed patency of the IMA to the heart without filling of cardiac veins. All dogs had infarcts in the distribution of the LADA; these infarcts were smaller in dogs with venous arterialization. The anastomoses were obliterated by mature or maturing fibrous tissue, with alteration of the vein so that it was frequently not discernible, while the IMA was well preserved. Distal veins had foci of intimal proliferation, subintimal fibrosis, and medial hypertrophy. Although venous arterialzaiton provides protection for the acutely ischemic myocardium, this effect does not persist, perhaps because of anastomotic occlusion due to fibrous proliferation.

Cold blood as the vehicle for potassium cardioplegia.

Cold blood with potassium, 34 mEq/L, was compared with cold blood and with a cardioplegic solution. Three groups of 6 dogs had 2 hours of aortic cross-clamp while on total bypass at 28 degrees C with the left ventricle vented. An initial 5-minute coronary perfusion was followed by 2 minutes of perfusion every 15 minutes for the cardioplegic solution (8 degrees C) and every 30 minutes for 3 minutes with cold blood or cold blood with potassium (8 degrees C). Hearts receiving cold blood or cold blood with potassium had topical cardiac hypothermia with crushed ice. Peak systolic pressure, rate of rise of left ventricular pressure, maximum velocity of the contractile element, pressure volume curves, coronary flow, coronary flow distribution, and myocardial uptake of oxygen, lactate, and pyruvate were measured prior to ischemia and 30 minutes after restoration of coronary flow. Myocardial creatine phosphate (CP), adenosine triphosphate (ATP), and adenosine diphosphate (ADP) were determined at the end of ischemia and after recovery. Changes in coronary flow, coronary flow distribution, and myocardial uptake of oxygen and pyruvate were not significant. Peak systolic pressure and lactate uptake declined significantly for hearts perfused with cold blood but not those with cold blood with potassium. ATP and ADP were lowest in hearts perfused with cardioplegic solution, and CP and ATP did not return to control in any group. Heart water increased with the use of cold blood and cardioplegic solution. Myocardial protection with cold blood with potassium and topical hypothermia has some advantages over cold blood and cardioplegic solution.

Reference wavelength method for a two-color pyrometer.

The reference wavelength method is used for a two-color pyrometer and, with the reference wavelength method, an analytical formula of the ratio temperature for the two-color pyrometer is derived. For one channel of the two-color pyrometer, with a triangular spectral response of 0.1-micro m FWHM and 2.0-micro m peak wavelength, the effective wavelength and the correction factors with several reference wavelengths are determined. By fitting the curves of the effective wavelength and the correction factor to simple functional forms of temperature, the radiance errors for both cases are calculated. Also, it is found that the correction factor determined in a single-color pyrometer can be used directly in one channel of the two-color pyrometer without additional calculation.

Relative phase control between two successive coherent anti-Stokes Raman-scattering signals for the recovery of spectral lines.

We have controlled the relative phase between two successively generated coherent anti-Stokes Raman-scattering signals with a homemade phase-shifting unit, the thickness of which could be automatically adjusted as the wavelength of Stokes beam scanned in a wide spectral range. With this technique we have recovered the Q-branch spectrum of carbon monoxide distorted by a large nonresonant contribution from propane. Also, we have selectively recorded the spectrum of hydrogen chloride buried in the spectrum of propane.

Four-pass amplifier for the pulsed amplification of a narrow-bandwidth continuous-wave dye laser.

We demonstrate a new type of four-pass dye laser amplifier that can reduce the possibility of parasitic oscillation between optical components used in the amplifier. Pumping the amplifier with a 5.6-mJ Q-switched doubled Nd:YAG laser output, we obtain high-peak-power pulsed output of an incident cw narrow-bandwidth dye laser beam with a power gain greater than 2 x 10(6) . Subsequent amplification of the pulse with a conventional dye amplifier yields 42% energy efficiency. When a temporally stretched pumping pulse is used, the eventual bandwidth of the final output is measured to be 130 MHz.

Suppression of amplified spontaneous emission from a four-pass dye laser amplifier.

We demonstrate a new design for a four-pass dye laser amplifier that can be used to reduce amplified spontaneous emission (ASE) in the amplifier output beam. Compared with the results obtained from normal operation of the four-pass dye laser amplifier without a frequency-selective device, by using a diffraction grating in the amplifier we can reduce the ASE ratio by a factor in excess of 10 and increase output energy by ~4%. The obtained ASE ratio of the four-pass amplifier system is <1.5%.

Fabry-Perot wavemeter for shot-by-shot analysis of pulsed lasers.

A Fabry-Perot wavemeter for analyzing a pulsed laser operating in a single longitudinal mode with an injection-seeding technique has been constructed with an array detector. This wavemeter permits the real-time measurement of both the wavelength and the spectral effectiveness of the laser pulse produced at 10 Hz. The performance of the wavemeter is checked with a frequency-stabilized He-Ne laser and a double Nd:YAG laser that operates in the single longitudinal mode. The precision of the wavemeter is found to be < 10 MHz. Also, we calculated the uncertainties in determining the wave number by processing a Fabry-Perot fringe pattern imaged on a linear-array detector. The calculation is done by changing the number of pixels of the array detector, the finesse of the Fabry-Perot étalon, the waist of the incident laser beam, and the magnitude of random noise.

Broadband coherent anti-Stokes Raman spectroscopy with a modeless dye laser.

We develop a modeless dye laser for broadband coherent anti-Stokes Raman spectroscopy (CARS) and investigate the operational characteristics of the modeless laser. The energy efficiency of the modeless laser is 6%, and the beam divergence is 0.65 mrad. We construct a compact movable CARS system with the modeless laser and a graphite tube furnace to assess the accuracy of the CARS temperature. It is found that the difference between the averaged CARS temperature and the radiation temperature measured with an optical pyrometer is <2% at a temperature range from 1000 to 2400 K. We also measure the averaged CARS temperature drift owing to the variation of the spectral distribution of the modeless laser, which is <1.5% during 5 h of operation.

A servo controlled transapical left ventricular to aortic assist device with implantable canulae.

A servo controlled transapical LV to aortic bypass system employing a roller pump was evaluated. The pump achieved complete LV decompression with reduction of LV pressure below systemic pressure. The servo control was responsive to LA pressure and allowed stable complete bypass during interventions designed to raise and lower LA pressure. A permanently implantable transapical LV cannula and aortic cannula without obturators was evaluated with and without anticoagulants. The teflon felt surface 'healed' rapidly and developed a multi-layered fibrous pseudointima. Anticoagulants appeared to avoid excessive thrombus formation at the cannula sites and embolization.

Broadband D2 coherent anti-stokes Raman spectroscopy for single-shot pressure and temperature determination with a Fabry-Perot etalon.

A method is demonstrated that employs a Fabry-Perot etalon to modulate a broadband coherent anti-Stokes Raman spectroscopy signal beam spatially to obtain enhanced resolution and spectral information for single-shot measurements of pressure and temperature. Resulting images are analyzed by; first, fits to Fabry-Perot patterns for single rovibrational lines; second, a line-shape analysis for a single rovibrational line; and third, a mapping of the Fabry-Perot channel spectra to a linear spectrum. Measurements of the D(2) Raman Q-branch lines were made for a D(2) in Ar mixture to take advantage of the large pressure shift and rovibrational line spacing. Peaks are located to better than 0.5% of the free spectral range of the etalon (approximately 0.01 cm(-1)) and a quantitative analysis of the pressure shifting and broadening is determined for the 1-10-MPa range. Finally, temperature and pressure determination using a band-fitting analysis is demonstrated.