Ventricular aneurysm: pressure-volume relationships of a physical model.

Static pressure-volume characteristics were determined in elastic sacs with aneurysms of varying radius and wall thickness. Increasing the radius of an aneurysm lowered the maximal pressure (Pmax) which could be generated by contraction and deformed the pressure-volume curves compared with an intact sac of the same thickness. Progressive decrease in the wall thickness of an aneurysm of a given size resulted in progressive loss of pressure generated by any degree of filling. The present results suggest that shape, size and structure of the aneurysm and of the boundary between the normal myocardium and the aneurysm may contribute significantly to the impairment of the development of intraventricular pressure, and hence affect the contractile dynamics of the heart.

Effect of posture on arterial pressures, timing of the arterial sounds and pulse wave velocities in the extremities.

We have recorded systolic and diastolic blood pressure, and the intervals between the QRS complex of the electrocardiogram and the Korotkoff arterial sound at systolic and diastolic pressure (QKs and QKd, respectively), at the brachial and posterior malleolar arteries, for normal subjects in the supine, standing, or head-down positions on a tilt table. These data make it possible to calculate an apparent mean pulse wave velocity. Results indicate: (1) when the subject is supine (0 degrees), brachial and posterior malleolar artery blood pressures are virtually identical; (2) upon standing (+90 degrees), both systolic and diastolic pressures in the foot are elevated by a mean of approximately 70 mm Hg, whereas brachial artery systolic pressure is unaffected and brachial diastolic pressure is raised 7 mm of mercury; (3) conversely, in the head-down (feet-up) position (-30 degrees) the blood pressure in the foot was decreased approximately 20 mm of mercury, whereas the brachial arterial pressure is again unaffected; (4) as one changes from the head-down to the supine to the standing positions, the mean QKs interval at the brachial artery was increased by 5 and 15 msec, respectively; (5) conversely, the arrival of the pulse wave in the leg was hastened, with QKd decreasing by 7 and then 18 msec. The effects of QKs were slightly smaller in the brachial artery but considerably larger in the malleolar artery, with a decrease of 16 msec and then 48 msec; (6) mean apparent pulse wave velocity increases from 9.1 to 10.9 to 17.6 m/sec, as one changes from -30 degrees to 0 degrees to +90 degrees.

Vasomotor escape from adrenaline, noradrenaline or acetylcholine in the dog hind limb.

The noradrenaline, adrenaline and acetylcholine-induced vasoregulatory escape was demonstrated in the vascular bed of intact of skinned and denervated dog's hind limb. Escape effect disappeared or decreased markedly under elevation tissue pressure in the examined hind limb. These data indicate that tissue pressure factor may take part in the mechanism of the escape phenomenon.

Ventilatory effects on pulmonary vascular inflow and outflow patterns.

Ventilation of an isolated lung lobe modifies the rate of inflow into its pulmonary artery (Murao and Rodbard, 1971). The present studies show that ventilation also influences the rate of outflow from the pulmonary vein in a manner which differs significantly from the effects on the rate of inflow into the pulmonary artery. Since this difference between instantaneous inflow and outflow rates affects the calculation of vascular conductance (resistance) and its interpretation we have compared and analysed the effects of ventilation on simultaneous flow patterns in the pulmonary artery and vein.

Effects of treadmill exercise on the timing of the heart and arterial sounds, and the slope of the brachial arterial pulse wave.

An indirect, noninvasive method of sphygmorecording was used to study the effect of exercise on a number of cardiac parameters, including heart rate, blood pressure, the timing of the heart and Korotkoff arterial sounds, and the slope (dP/DT) of the brachial arterial pressure wave. The QKd interval is a sensitive and reliable indicator of the cardiovascular response to exercise stress, and can be used to follow the rate of return to basal levels. Changes in the QKd can occur even in the presence of fixed heart rate. These studies provide a baseline for analysis of patients with cardiovascular disease.

Delayed timing of heart and arterial sounds in patients with implanted pacemakers.

We have recorded the timing of the heart sounds and the arterial sounds with reference to the onset of each cardiac cycle in 16 patients before and after implantation of a pacemaker prosthesis, and in an additional 18 patients after pacemaker implantation only. The interval between the QRS complex and the Korotkoff sound at diastolic pressure (QKd) is markedly prolonged, from 206 to 294 msec., a change corresponding to 10 standard errors of the mean difference. Likewise, the Q-Korotkoff interval at systolic pressure (QKs) is prolonged from 329 to 414 msec. The interval between the QRS complex and the onset of the first sound (S1) is prolonged by approximately 90 msec., whereas the interval between the QRS and the second heart sound (S2) is prolonged by 70 msec. We noted an associated increase in heart rate, a slight decrease in systolic pressure, an increase in diastolic pressure, a decrease in pulse pressure, and a slight decrease in the deltaP/deltat at the brachial artery measured indirectly and noninvasively.

Arterial stenosis, pressure, and flow.

The interaction between the effects of an arterial stenosis and postocclusion hyperemia was studied in a model of the capillaron system. A capillaron is a module consisting of soft-walled permeable vessels (capillaries) in a compliant capsule. Stenosis reduced flow in accord with arterial cross-sectional area. Addition of a capillaron reduced flow to a basal level. In this basal state, autoregulation and postocclusion hyperemia could be studied. Basal flow and autoregulation give no indication of the severity of the stenosis. The magnitude of the postocclusion hyperemia varied with the arterial pressure and, inversely, with the stenotic orifice area. In the absence of arterial pressure changes, the magnitude of the postocclusion hyperemia indicates the severity of the stenosis.

Pulmonary artery dissection and rupture in Eisenmenger's syndrome.

A patient with ventricular septal defect and pulmonary arterial hypertension (Eisenmenger's syndrome) associated with aortic coarctation with follow-up for 19 years, and with rupture of an aneurysmatic pulmonary artery is described. An incident of extreme fright with a possible transient systemic hypertension may have precipitated the dissection of the pulmonary arterial intima and the rupture.

Clinical utility of the simultaneous recording of heart and Korotkoff sounds.

Heart and arterial sounds and murmurs for a sequence of as many as 100 successive beats are recorded on a single print. The apparatus consists of a cathode ray oscilloscope, a Q-wave trigger to release the beam, a vertical axis which is connected to the blood pressure cuff, and an intensity modulation circuit which determines the intensity of the beam at each instant. This arrangement eliminates the baseline and thereby permits the display of low intensity acoustic signals. Data on normal subjects, and patients with various heart diseases are illustrated. Advantages and limitations of the method are discussed.

Compartments and suborgans of the ventricular myocardium.

Color-coded liquid plastic was injected intraparenchymally (not into the blood vessels) into more than 300 hearts of homeotherms--including dog, cat, sheep, beef, horse, mammalian dolphins, chickens, turkeys, etc. The organization of the hearts of all these species appears to be similar. After injection of a heart segment such as the right ventricular free wall, corrosion (digestion) of the heart in strong alkali releases the case of only this free wall, and of the lymphatic vessels which drain this segment. None of the injected plastic enters the left ventricular free wall or the septum. Color-coded injections reveal that injections into only the left ventricular free wall, followed by digestion of the heart releases a cast of only the left ventricular free wall. Injection into the septum produces a cast of only the septum. Injection into all three compartments provides a cast of the apex and midpoint of the heart. The colors and injections remain discrete--they never mix. This is evidence that fibrous supercapsules separate these three compartments. The casts prepared by injection into the middle or inferior parts of the ventricular myocardium show large lacunae at the base. Similar injection experiments show that the base of the heart consists of two discrete suborgans: the inflow tract or cushion (tricuspid and mitral rings, and their papillary muscles), and the outflow tract or infundibulum (muscular bundles inferior to the pulmonary and aortic outlets). Further studies showed that the septum consists of discrete right and left hemiseptae. These data support the hypothesis that the heart consists of three suborgans; the cushion, venter (pump), and infundibulum. Each suborgan consists of four compartmetns: its free right wall, free left wall, and right and left hemiseptae. These entirely separate twelve compartments of the ventricular myocardium are held together by strong fibrous connective tissues. Their function is coordinated by the atrioventricular conduction system. The present studies indicate that earlier studies which have indicated that the heart consists of one or two bandage-like, concentric wrappings may be incorrect. The significance of our findings is dicussed.

Orientation of the fascicles of the ventricular myocardium.

A new technique was developed to examine the arrangement of the fascicles of the myocardium. Liquid plastic was injected intramurally into the free walls and the septum of more than 300 hearts of mammals and birds. After the plastic hardened, the tissues were digested in alkali, thereby releasing a plastic cast which had been formed in the myocardium. The plastic plates formed in the heart were consistently perpendicular to the surfaces of the epicardium and the endocardium. Related studies have shown that each cluster or clone of muscle fibers is contained in a fibrous connective tissue capsule. The injected plastic is therefore confined to the trabecular (extracapsular) clefts which define the borders of the capsules. The casts show that the capsules containing the muscle fibers are arranged in the planes of great circles of the myocardial spheroid. These capsules are shaped as wedges with acute angles at the endocardium, and with dihedral angles less than 1 degree. Interventricular sulci interrupt and separate the capsules of the right free wall from the left free wall. Septal capsules are separated from but aligned with the long directions of the capsules of the adjacent free walls. These data challenge the currently accepted concept of the bandage-like arrangement of the myocardial fascicles. The significance of our findings with respect to myocardial function is discussed.

Venous pressure and exercise tolerance.

Compared to the number of contractions obtained when a blood pressure cuff on the upper arm was at zero pressure, inflation of the cuff to pressures ranging between 5 and 40 mm Hg resulted in an augmentation of the number of hand contractions that could be performed prior to the development of ipsilateral severe fatigue or intolerable pain. Cuff pressures of 60 mm Hg reduced the number of contractions below the control level. These results are consistent with the concept that exercise during venous congestion facilitates the washout of the toxic catabolite presumed to be produced during muscular contraction.

Factors affecting the transvalvar pressure difference in a hydraulic model of aortic stenosis.

Mechanical factors that can modify the peak transvalvar pressure differences (delta P) in aortic stenosis were evaluated in a model. A latex rubber sac simulated the ventricle. Expansion of the walls of the sac by means of a negative pressure applied to its outer wall introduced a measure volume into the sac and placed the wall materials under tension. The stretched sac was then permitted to contract and to expel its contents through "aortic valvar" orifices of various severities of stenosis, into an aortic standpipe of selected diameters (compliances). Factors that increased the peak delta P included the strength (thickness) of the ventricular wall, the rate at which it mobilized and applied its tensile force to compress the sac contents, the unstressed volume of the sac, the total volume in the sac at onset of contraction, the severity of the valvar stenosis, the compliance of the aorta, the rate of arterial run-off, and the aortic diastolic pressure. Loss of forward stroke volume due to mitral regurgitation lowered the peak delta P. Elevations in diastolic arterial pressure also lowered delta P. All of these mechanical factors should be considered in the analysis of the severity of clinical aortic valvar stenosis and in decisions for medical therapy and surgical correction. The several factors which do not depend directly on the orifice area or on the forward stroke volume vitiate the sole use of the orifice formula in the analysis of the dynamics of aortic stenosis. The application of this approach in related problems is indicated.

Valve dynamics.

Flow between two contiguous elastic sheets (valve leaflets) generates one of two types of behavior. At low pressure differences, e.g. 1 cm H2O, the sheets part slightly and the fluid passes silently between them. The aperture under these silent conditions varies with the square of the length of the orifice, the transvalvular pressure difference and the kinetic energy, divided by the thickness of the leaflets. At higher transvalvular pressure differences the downstream end of the bicuspid valve alternately closes and reopens (flitter), and functions as an acoustic oscillator. The recurrence rate of flitter varies with the tension on the leaflets and inversely with the thickness. The threshold of the onset of flitter varies with the product of the pressure and the square of the length of the valve aperture, divided by the wall tension and thickness. The significance of these data in the onset of the flitter and of the recurrence rate is discussed in terms of the production of sounds and murmurs at the heart valves, vocal cords and other sites.

Mathematical formulation of post-occlusion hyperaemia and autoregulation of blood flow in the capillaron model.

A mathematical formulation of the blood flow behaviour through a capillaron model is described. The formulation is applied to the analysis of post-occlusion (reactive) hyperaemia and autoregulation.

Selective staining of fibrous connective tissue capsules and lymphatics: an evaluation of "interstitial" fluids.

Ringer's solution containing ferrocyanide ion was infused into the arterial system of lumbs. Some of these ions filtered across the blood capillary wall into the adjacent extracapillary fluids, from which diffusion caused these ions to enter the wall of the enclosing epimysial capsule. Ringer's solution containing ferric ion was then injected into the parenchyma (not intravascularly). In muscles, the intensely blue ferric ferrocyanide (Prussian blue) precipitate appeared on the walls of the fibrous connective tissue capsules that enclosed each small cluster of muscle cells, and in the lymphatics of the extracapsular clefts. No Prussian blue appeared inside the capsules. These results indicate that "interstitial" fluids are divided into two discrete pools: (a) an intracapsular pool of capillary ultrafiltrates, and (b) an extracapsular pool in the trabecular clefts. Certain implications concerning the mixing of the tissue fluids, the estimate of capillary filtration rates and some of the functional differences between intravascular and intramuscular injections are discussed.