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At least 73 records · Page 4Linked to original sources
PubMed1990

Potential application of new imaging modalities in the measurement of cardiac volumes and characteristics.

Developments of various imaging modalities in recent years have resulted in imaging systems with greater spatial resolution, faster data acquisition, and more powerful computer processing. It is the purpose of this report to examine three of these systems, positron emission tomography (PET), magnetic resonance imaging (MRI) and ultrafast computed tomography (cine-CT) with respect to their applicability for determination of cardiac volumes and other characteristics related to hypertension. While each of these modalities has widespread applications and specific advantages, this report will be primarily concerned with two objectives: functional ability to record indicator dilution curves suitable for quantification of flow and the anatomic or geometric ability to measure chamber dimensions with high accuracy. Time concentration curves have been outlined on all modalities and used for quantification of myocardial perfusion and myocardial reserve. Only one modality, cine-CT, determined cardiac output by dilution curves although in vivo arterial recording from PET has demonstrated suitable curves for this application. Both MRI and cine-CT have demonstrated accurate determination of chamber volumes by the geometric method, the latter giving somewhat higher spatial resolution. The advantages of these machines for such purposes have yet to be determined.

Cardiac Output↗
PubMed1994

Assessment of cardiac volumes and left ventricular mass by cine computed tomography before and after mitral balloon commissurotomy.

We used cine computed tomography (CT) to determine whether decreased mitral valve gradients and pulmonary artery pressures resulted in decreased right ventricular and atrial volumes after percutaneous mitral balloon commissurotomy (MBC). In patients treated for severe mitral stenosis, previous studies have shown that after the mitral valve gradient decreases, the left atrial volume is reduced and left ventricular stroke volume is increased. The effects of commissurotomy on right heart chamber sizes have been difficult to assess with angiography and echocardiography. Moreover, in follow-up studies performed after surgery, changes in cardiac chamber volumes occurring after the mitral valve gradient and pulmonary pressure are reduced are confounded by the effects of thoracotomy. Our group has previously demonstrated that cine CT can accurately measure both left and right cardiac chamber volumes. We studied 11 female patients before, immediately after, and at 1 year after MBC, and 9 female control subjects of comparable age. To assess cardiac chamber volumes, we used cine CT. To assess the effects of MBC, we used cardiac catheterization and Doppler echocardiography.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1993

Cardiac volume receptor reflex in borderline hypertensive rats.

With increased dietary NaCl intake (8% NaCl), borderline hypertensive rats (BHR) develop hypertension and exhibit an exaggerated natriuresis in response to intravenous isotonic saline volume expansion. The exaggerated natriuresis is mediated by the concurrent exaggerated withdrawal of efferent renal sympathetic nerve activity since prior renal denervation eliminates the exaggerated natriuretic response. It was the objective of the present study to examine cardiac volume receptor reflex control of efferent renal sympathetic nerve activity in BHR made hypertensive by increased dietary NaCl intake. BHR were fed either 1% or 8% NaCl from age 4 to 16 weeks. BHR fed 8% NaCl were hypertensive (148 +/- 9 mmHg) compared with BHR fed 1% NaCl (115 +/- 6 mm Hg, p < 0.05). In one protocol, measurements of right atrial pressure and efferent renal sympathetic nerve activity were made in sinoaortic-denervated BHR before and during a 10% body weight intravenous isotonic saline volume load. Compared with 1% NaCl BHR, 8% NaCl BHR showed both a greater maximal inhibition of efferent renal sympathetic nerve activity (-67 +/- 4% versus -31 +/- 3% of control, p < 0.05) and gain (-22.0 +/- 2.3 versus -9.7 +/- 1.7%/mm Hg, p < 0.05). In a second protocol, measurements of efferent renal sympathetic nerve activity were made in sinoaortic-denervated BHR before and during graded frequency stimulation of the central portion of the sectioned vagus nerve.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1975

[Method of continuous monitoring of stroke and minute cardiac volume by the aortic pressure curve].

A new method of determining the cardiac output and stroke volume on the basis of the aortic pressure curve by way of a direct pressure-volume calibration is suggested. For this purpose two catheters are introduced into the ascending aorta, and via one of them saline is supplied with a constant volume rate (delta V). At the same time the augmentation of the diastolic pressure in the aorta (delta P) caused by the administration of the saline is recorded by means of the second catheter which tip is located some 3--4 cm below the first one along the blood flow. The mean pulse pressure in the aorta (Pp) also corresponds to a definite flow in the aorta (V). The relationship between the volume and pressure in the aorta within the physiological range is a lineal function. Hence, V = Pp-delta V divided by delta P cm3/sec. By multiplying this value times the duration of the cardiac cycle in seconds, the stroke volume is obtained. By dividing the volume of the administered saline (delta V.t) into the pressure augmentation area (delta S), the volume corresponding to each unit of the pressure area is found. Then by multiplying this calibration value times the area under the pressure curve in any cardiac cycle (S) again the stroke volume is obtained: Vstr = S-deltaV-t divided by delta S cm3. By a continuous recording of the mean pulse pressure in the aorta and of the full pressure curve it is possible to conduct a continuous control of the stroke volume and cardiac output using the preliminarily obtained calibration value. The suggested method permits to determine the filling of the aorta below the coarctation, the blood return from the aorta into the left ventricle in cases of aortic insufficiency, as well as the elastic properties of the aorta. An attempt was made to substitute the recording of the volume pulse and left arm rheopletysmography for the recording catheter.

Aorta↗