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Biomedical subjects

D G Mathey

Publications and source records attributed to D G Mathey.

80 records · Page 5Linked to original sources
PubMed1978

Pronounced dependence of ventricular endocardial QRS potentials on ventricular volume.

To evalulate the relation between ventricular endocardial potentials (QRS amplitude) and ventricular dimensions, left and right ventricular endocardial potentials were recorded with hook electrodes in anaesthetised open-chest dogs during transfusion and withdrawal of blood. Left ventricular end-diastolic diameter was measured by ultrasonic crystals, and end-diastolic volume was determined by thermodilution. In each dog, left ventricular endocardial potentials, whether recorded from anterior or posterolateral walls, decreased linearly as left ventricular end-diastolic diameter or volume increased, and vice versa. With an average increase in left ventricular end-diastolic diameter from 40.1 +/- 1.7 to 44.6 +/- 1.8 mm, left ventricular endocardial potentials decreased from 32.8 +/- 2.5 to 23.5 +/- 2.3 mV (P less than 0.001); and for an increase in left ventricular end-diastolic volume from 1.36 "/- 1.25 to 3.43 +/- 0.58 ml/kg left ventricular endocardial potentials decreased from 36.2 +/- 6.6 to 14.9 +/- 4.3 mV (P less than 0.001). Changes in right ventricular endocardial potentials paralleled the changes in left ventricular endocardial potentials. These findings indicate that acute changes in ventricular dimensions influence endocardial potentials considerably, and suggest a potential clinical application for detecting acute changes in ventricular volume.

Action Potentials↗
PubMed1978

Segment stroke work and metabolism depend on coronary blood flow in the pig.

We determined the mechanical and metabolic effects of graded myocardial ischemia in 23 open-chest, anesthetized pigs. By connecting the midportion of the left anterior descending artery (LAD) to the carotid artery via a constant volume, calibrated pump, we reduced the flow in the LAD to 0, 25, 50, and 75% of control rates for periods of 1 h. Flows of 100% and 150% were also examined. Using pairs of ultrasonic crystals to measure segment dimensions, we calculated segment shortening and thickening, and total and systolic stroke work in the ischemic and normally perfused segments. Blood gases, pH, and lactate and inosine balances were determined from the regional coronary venous blood. At coronary blood flows of 0, 25, 50, and 75% of normal resting flow, total segment work was 8 +/- 8, 25 +/- 4, 51 +/- 5, and 80 +/- 6% of control, respectively, while systolic segment work was -2 +/- 5, -10 +/- 5, 40 +/- 5, and 86 +/- 7% of control, respectively (means +/- SE). Thus, the decrease in total segment stroke work is proportional to the decrease in flow over the range 0-100%. However, no useful work (i.e., systolic work) is done until flow exceeds 25%. Segment shortening and thickening are significantly depressed with flows diminished by only 25%. Segmental inosine production correlates with lactate production and parallels decreased mechanical performance.

Animals↗
PubMed1978

Coronary sinus reflux. A source of error in the measurement of thermodilution coronary sinus flow.

In seven patients thermodilution coronary sinus flow (TD-CSF) was higher (164 +/- 21 ml/min) during ventricular pacing than during atrial pacing (119 +/- 21 ml/min, P less than 0.005) at identical heart rate, without an increase in the determinants of myocardial oxygen consumption. To assess the possibility of right atrial admixture in coronary sinus blood during ventricular pacing we compared electromagnetic coronary arterial blood flow (CBF) with TD-CSF in nine dogs during interventions that increased right atrial pressure. During ventricular pacing, rapid atrial pacing, pulmonary artery constriction and increased intrathoracic pressure, right atrial pressure increased and electromagnetic CBF was significantly less (41-166%) than TD-CSF. Marked reflux from the right atrium to the coronary sinus was also demonstrated by bolus injection of cold saline into the right atrium and continuous infusion of contrast material into coronary sinus. Caution needs to be exercised in interpreting TD-CSF in the presence of changing right atrial pressure.

Adult↗
PubMed1977

Abnormal left ventricular contraction pattern in the systolic click-late systolic murmur syndrome.

A contraction abnormality of the left ventricle has previously been described in patients with systolic click-late systolic murmur syndrome. To determine if the contraction abnormality is present in the preprolapse period, LV dimensions and the instantaneous velocity of circumferential fiber shortening (VCF) were studied in 18 patients with the mitral valve prolapse and 16 normal subjects using computer analysis of echocardiograms. VCF attained its maximum (max VCF) during the preprolapse period an average of 94 msec before the mid-systolic click. Max VCF was significantly reduced in patients with mitral valve prolapse (2.06 vs 2.55 circ/sec in normal subjects, P less than 0.001). Despite the reduction in max VCF, no difference in the extent and percentage of diameter shortening was found between patients and normal subjects. This discrepancy is explained by a sustained rate of mid-to-late systolic diameter shortening in the presence of mitral valve prolapse as manifested by a typical VCF profile (P less than 0.001) and a longer duration of diameter shortening (353 vs 306 msec in normal subjects, P less than 0.01). The decrease of max VCF in patients with mitral valve prolapse suggests a reduction in LV contractility. Since the abnormality is present in the preprolapse period, it is unrelated to a direct mechanical effect of the prolapse itself. Additional fiber shortening in mid-to-late systole indicates that the sudden displacement of the mitral leaflets may have an unloading effect on the left ventricle.

Adult↗
PubMed1976

The determinants of onset of mitral valve prolapse in the systolic click-late systolic murmur syndrome.

The onset of mitral valve prolapse and its close correlate, the time of systolic click, vary considerably with different physiologic and pharmacologic interventions. In order to explain the mechanism responsible for these alterations, the effects of tilt and amyl nitrite inhalation on left ventricular dynamics and the time of the systolic click were studied by analyzing echocardiograms and simultaneously recorded phonocardiograms in 14 patients with mitral valve prolapse and mid-systolic click. The patients were studied in the supine position, with 40-60 degrees head-up tilt and after amyl nitrite inhalation. Computer analysis of the recordings was used to measure the left ventricular end-diastolic diameter, the click diameter (left ventricular diameter at the time of mid-systolic click), the maximal velocity of circumferential fiber shortening (max VCF), and the time interval between the first heart sound and systolic click (S1-X). With tilt and amyl nitrite, shortening of the S1-X interval b y an average of 44 and 87 msec, respectively, was observed. The click diameter, however, remained virtually constant with both maneuvers. Earlier prolapse after tilt was due to a decrease in the end-diastolic diameter from 5.03 +/- 0.74 to 4.50 +/- 0.68 cm (P less than 0.001) with no change in max VCF. Immediately after amyl nitrite, earlier prolapse was due to an increase of VCF in the preprolapse period, with max VCF increasing from 2.15 +/- 0.27 to 3.06 +/- 0.40 circ/sec (P less than 0.001), there being no change in the end-diastolic diameter up to this time. The constant click diameter indicates that the abnormal valve motion in this syndrome occurs at a critical left ventricular chamber size. Variations in the onset of prolapse are caused by changes in left ventricular end-diastolic dimensions and the velocity of circumferential fiber shortening in the preprolapse period.

Adult↗
PubMedDate not supplied

Lack of correlation after reperfusion between ventricular function and infarct size estimated by thallium single-photon emission computed tomography.

In 32 patients with acute myocardial infarction, who had undergone successful intracoronary thrombolysis, the results of regional wall motion measured from contrast cineangiograms 10 to 21 days after thrombolysis were related to the results of thallium single-photon emission computed tomography (SPECT) after intravenous dipyridamole. Wall motion was measured by means of the centerline method, and thallium defect size was estimated by comparing the patient's circumferential profile with that of 20 normals. No correlation was found between ejection fraction or regional wall motion and thallium defect size. The time from symptom onset to thrombolysis was inversely correlated with the degree of hypokinesis (r = -0.51) but not with thallium defect size. In patients treated within 3 hours, hypokinesis was significantly less than in patients treated later (-1.1 +/- 0.6 SD vs -2.2 +/- 0.8 SD, p less than 0.01) whereas thallium defect size was not significantly different in both groups. It is concluded that, in patients after thrombolysis, thallium defect size determined by SPECT does not reflect the degree of left ventricular dysfunction.

Adult↗