Peter R. Lynch

Cardiac Function During Left Coronary Arteriography in Canines with Ioxaglate, Nonionic Compounds, and Diatrizoate

The new contrast medium ioxaglate (P286) was compared with diatrizoate and the nonionic media metrizamide and C-29 regarding their effects on left ventricular pressure, the rate of rise in this pressure (dP/dt), stroke volume, peak aortic flow rate, and on the QT interval during left coronary arteriography in dogs. Ioxaglate and the nonionic compounds had significantly less effect on these parameters than diatrizoate. Contractility and QT time was least affected by the nonionic media, which have an osmolality similar to that of ioxaglate. This indicates that, in addition to osmolality, other properties of contrast solutions contribute to their toxic effects on the heart. Measuring contractility seems to be a more sensitive method in evaluating contrast media than measuring the performance of the heart as a pump.

Mechanism of Production of Cardiac Conduction Abnormalities Due to Coronary Arteriography in Dogs

Left coronary arteriography and left coronary artery injections of Tyrodes solution and glucose solutions were performed in 12 anesthetized dogs. The contrast medium was found to prolong the conduction time through the AV junctional tissue and through the most distal part of the conduction network as verified by His-bundle electrogram and by surface ECG (lead II). The results indicate that for evaluation of the effects on conductivity of various media, it is most reliable to measure the altered conduction velocity in the AV nodal region. The prolongation of conduction time produced by contrast medium explains heart conduction blocks and may contribute to the genesis of ventricular fibrillation, frequent complications to coronary arteriography. The data suggest that anoxemia does not cause this delayed conduction. Hyperosmolarity contributes to the alterations of the conductivity, but the ionic composition and anion toxicity of the contrast medium also may be of importance.

THE EFFECTS OF NICOTINAMIDE AND HYPERBARIC OXYGEN ON SKIN FLAP SURVIVAL

Hyperbaric oxygen has been established as an acceptable treatment for the chronic healing wound. Nicotinamide has been shown to be angiogenic and accelerate the physiologic process following wounding. Therefore both nicotinamide and hyperbaric oxygen were evaluated to enhance flap survival in an island pedicle skin flap model. These two treatment modalities were evaluated alone and in combination to assess if there is an addictive effect to enhance flap survival. Forty Sprague-Dawley male rats (weight 300-350 grams) were treated for 14 days preoperatively 1 day post-operatively with either 400 mg of nicotinamide i.p. or saline i.p. On day 14, a 7 X 7 cm island pedicle skin flap was elevated ligating the left inferior epigastric neurovascular pedicle and were sutured in their normal position. Twenty animals then underwent hyperbaric oxygen treatments. Forty-eight hours post-operatively animals were re-anesthetized and were given a single injection of fluorescein (25 mg/kg) via the tail vein. The % survival of the flap and SEM of the groups are as follows: Saline 45.67 +/- 31.14, nicotinamide 85.30 +/- 9.24, saline-hyperbaric oxygen 76.70 +/- 9.42 and nicotinamide-hyperbaric oxygen 90.86 +/- 3.94 with statistical significance of p less than 0.01. Nicotinamide appears to be another acceptable therapeutic modality in the management of the acceleration of wound healing.

Coronary Arteriography in Canines with Calcium-Enriched Ioxaglate and Diatrizoate

Ioxaglate, diatrizoate, and calcium-enriched solutions of these contrast agents were compared as to their effects on left ventricular pressure, the first derivative of this pressure, left ventricular stroke volume, stroke work, and mean aortic pressure during left coronary arteriography in dogs. Ioxaglate reduced these parameters significantly less than did diatrizoate. The calcium addition ameliorated the toxic effects of both ioxaglate and diatrizoate. There was an initial reduction of stroke work during and following the contrast injections, after which increased stroke work was observed. The calcium ions did not produce further augmentation of this increased stroke work.

Responses of canine jugular veins and carotid arteries to hysterectomy: Increased permeability and leukocyte adhesions and invasion

Abstract Events which initiate postoperative deep venous thrombosis occur in the intraoperative or early postoperative period in patients undergoing major surgery. Also endothelial alterations and accumulation of blood cells and noncellular material were observed in canine veins 4 hr. after splenectomy, hysterectomy and intestinal anastomosis. In the present investigation we examined canine jugular veins and carotid arteries 1 hr. after hysterectomy. Hysterectomy increased the amount of plasma (as measured by 125 I-labeled protein) in interstitial space of veins and arteries 3.6-fold over control values. In control vessels mg plasma/gm vessel were: jugulars, 23 and carotides 14, and 1 hr. after hysterectomy: jugulars 78 and carotids 52. Differences were significant at the 0.02 level. Scanning electron microscopy showed that endothelium of control veins was smooth and free of adhering blood elements while endothelium of posthysterectomy dogs had extensive pseudopods, blebs and pits. Adhering and invading leukoctyes were found on all postsurgical veins singly or in small patches. Despite increased permeability postsurgical arteries were free of blood cells and little affected at the electron microscopic level. This model resembles clinical postoperative deep vein thrombosis in that vessels to be studied were distant from the surgical site and were not damaged directly. We suggest that the changes caused by blood born products of tissue injury may represent the venous lesion that contributes to the initiation and propagation of deep venous thrombosis, other conditions being favorable. Failure of blood elements to adhere to arteries may help explain their resistance to postoperative thrombosis.

A Comparative Study of Various Single-Plane Cineangiocardiographic Methods to Measure Left-Ventricular Volume

Monoplane angiocardiographic methods are widely used to measure left-ventricular volumes (LVVs). Generally, the ellipsoid and Simpsons rule models are used to calculate LVV. Due to the assumed circular cross-sectional area of the left ventricle, both models have a fundamental error which theoretically prohibits the exact calculation of LVV. In this paper, a method to reduce this fundamental error is suggested whereby the LVV is calculated by Simpsons rule, but with each truncated cone or frustum multiplied by a correction factor to relate the assumed circular cross-sectional area to the true cross-sectional area of the frustum. The developed correction-factor technique is compared to the currently used ellipsoid and the Simpsons rule models for 18 canine left-ventricular casts, and the results show that the correction-factor technique has a greater accuracy than any of the conventional methods.

Frequency analysis approach to the origin of the first and second heart sounds

Catheter-tipped micromanometers were used to simultaneously record left ventricular and aortic pressures, and left ventricular and aortic internal phonocardiograms in order to determine if they had a common mode of origin and propagation. Spectrographic analysis showed that even with high-pass filtration the phonocardiogram obtained with a commonly used system (Millar) contained large amounts of energy in the subaudible frequency range (below 40 Hz). It was possible to derive close facsimiles of the phonocardiograms by double differentiation of the corresponding pressure pulse and conversely to derive the pressure pulse by double integration of the phonocardiograms. The propagation velocities of the first heart sound, second heart sound, and the foot of the aortic pressure pulse were found to be similar and were respectively, 4.3 +/- 0.2, 4.6 +/- 0.3, and 4.2 +/- 0.2 m/sec (+/- SE). These data support the concept that the low frequency pressure variations produced by the heart, which predominate in the left ventricular and aortic pressure pulse waveforms, are generated and propagated in the same manner as the high frequency pressure variations, which are the first and second heart sounds.

Cineradiographic frame rate selection for left ventricular volumetry.

The left ventricular volume curve was plotted from biplane cineangiograms at 270 frames per second, using Simpsons rule to measure the volume. Fourier transformation was applied to obtain the frequency spectrum of the curve. Volume curves at slower rates were produced. Curves with less than 5% error can be generated at 15 frames per second because of the low frequency content. This rate of filming was adequate to measure left ventricular volume by biplane cineradiography.

Cardiovascular and respiratory studies on skin divers following physical training.

Twenty-seven scuba divers were studied to determine the level of physical fitness before and after four months’ training. Studies included an exercise-tolerance step test, vital capacity (VC), maximum voluntary ventilation (MVV), functional residual capacity (FRC), total lung capacity (TLC), expiratory reserve volume (ERV), residual volume (RV), resting and stress blood pressure (BP), and the reflex bradycardia associated with diving. The results revealed an improvement In conditioning as measured by the step test. The ratio of RV to TLC diminished; MVV, VC and ERV increased. Resting BP diminished in both conditioned and unconditioned groups. Resting pulse rate did not change. Bradycardia with face submersion was found to be prominent in the conditioned group, although statistical significance was borderline. A short training period appears useful in improving physiologic functions of divers and is suggested as a safety measure.

Superior mesenteric artery occlusion in dogs: A model to produce the spectrum of intestinal ischemia

Abstract A surgical model in dogs, which can reliably simulate the spectrum of changes seen in intestinal ischemia in man by varying the length and extent of ischemic bowel, is presented. Ischemia of a precise segment of bowel was produced by ligation and transection of a branch of superior mesenteric artery. Dogs with ischemia of 60 cm or less of the bowel survived, and the bowel showed no ischemic changes, whereas ischemia of 110 cm or more of the bowel was not compatible with survival and generally resulted in infarction. The intermediate group with ischemia of 65–105 cm of the bowel revealed significant ischemic changes with ulceration and occasionally stricture formation.