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Biomedical subjects

G C Derby

Publications and source records attributed to G C Derby.

34 records · Page 2Linked to original sources
PubMed1987

Long-term follow-up after surgical correction of Wolff-Parkinson-White syndrome.

The long-term efficacy of surgical correction of Wolff-Parkinson-White syndrome was evaluated in 45 consecutive patients. Before surgery, 42 patients had reciprocating tachycardia and 12 had atrial fibrillation. The principal operative procedure was endocardial incision in 42 patients, endocardial cryoablation in 2 patients and epicardial cryoablation without dissection of the atrioventricular (AV) fat pad in 1 patient. Two patients had perioperative complications. One patient had bleeding that necessitated reoperation, and one had a right cerebral stroke with subsequent clearing of neurologic deficit. At postoperative electrophysiologic study, only the patient who underwent epicardial cryoablation had conduction over an accessory connection. Two others had intermittent delta waves in the early postoperative period but no accessory connection conduction at electrophysiologic study. During a mean follow-up of 3.1 years, the patient with ineffective cryoablation had recurrent orthodromic tachycardia, and one other patient had late recurrence of delta waves without arrhythmias. Four other patients had frequent palpitation, which was caused by premature ventricular complexes in three and sinus tachycardia in one. Seventeen patients had occasional "skipped beats" without recurrence of tachyarrhythmias. Twelve of 13 patients whose arrhythmias limited employment before surgery returned to work after surgery. By actuarial analysis at 1, 2 and 3 years, all patients were alive and 98% were free from tachyarrhythmias. Surgical correction of Wolff-Parkinson-White syndrome provides excellent long-term results with low morbidity. Patients who are disabled by arrhythmias return to work after successful surgery. Delta waves may persist or recur without return of arrhythmias. Minor postoperative episodes of palpitation are common and do not correlate with tachyarrhythmias.

Endocardium↗
PubMed1987

Relative contributions of the anterior and posterior mitral chordae tendineae to canine global left ventricular systolic function.

The relative importance of the anterior and posterior mitral chordae tendineae to global left ventricular performance, independent of load, was determined by sequentially measuring the slope of the left ventricular peak isovolumetric pressure-volume relation in a canine model with the chordae of both, either, and neither mitral leaflet(s) intact. The order in which the chordae were severed was randomly assigned. Compared to baseline values (both chordae intact), severing the chordae of the anterior leaflet (posterior leaflet chordae intact) reduced the slope of the pressure-volume relation by 27% (p = 0.005) in 10 dogs; the slope decreased by an additional 16% (p = 0.017) when the posterior chordae were subsequently severed in this group. In 10 dogs randomized to the reverse order, the slope of the pressure-volume relation decreased by 17% (p = 0.021) after the posterior chordae were severed (anterior leaflet chordae intact); an additional 24% decrease in the slope (p = 0.001) occurred when the chordae of the anterior leaflet were subsequently severed in this group. The chordae of the anterior and posterior mitral leaflets have an additive, but statistically indistinguishable (p = 0.140), influence upon global left ventricular systolic performance; however, the contribution of the anterior chordae tends to be more important. Thus preservation of the anterior mitral leaflet and its chordal attachments to the papillary muscles during mitral valve replacement may have an equal or greater impact upon postoperative left ventricular function than mitral valve replacement with preservation of the posterior chordae; however, severing either the anterior or posterior chordae appears to be detrimental.

Animals↗
PubMed1986

Valvular-ventricular interaction: importance of the mitral apparatus in canine left ventricular systolic performance.

As the mitral valvular apparatus tenses during systole, forces transmitted along the chordae tendineae to the left ventricular chamber may influence left ventricular performance. To test this hypothesis, 10 dogs anesthetized with fentanyl were studied during cardiopulmonary bypass. The importance of the mitral apparatus in left ventricular systolic function was assessed independent of load by means of the slope of the contractile state-dependent left ventricular peak isovolumetric pressure-volume relationship (Emax), which was measured at constant heart rate and aortic pressure with a micromanometer inside a left ventricular intracavitary balloon before and immediately after all chordae tendineae were severed. Herniation of the balloon was prevented by a disk secured to the mitral anulus. Emax decreased from 11.97 +/- 3.35 (+/- SD) to 6.38 +/- 0.96 mm Hg/ml (p less than .001) with chordal severing. The volume intercept (Vo) was unchanged. Fluoroscopic studies of the balloon contour in eight additional dogs revealed dyskinesia in the area of the papillary muscle insertion and substantial alterations in chamber geometry during systole after the chordae were severed. Accordingly, we conclude that global left ventricular systolic performance is impaired when chordal attachments of the mitral valve are disrupted. Changes in left ventricular geometry or loss of inward force normally transmitted to the left ventricular wall as the valve tense may underlie these changes. These findings suggest that postoperative left ventricular dysfunction after mitral valve replacement may be attributable, in part, to excision of the native mitral apparatus at the time of surgery and support efforts to spare chordae during mitral valve surgery.

Animals↗
PubMed1986

Results of operations for ventricular tachycardia in 105 patients.

Operations to treat ventricular tachycardia refractory to antiarrhythmic drugs were performed in 105 patients. Intraoperative epicardial activation sequence maps were completed in 83% and endocardial maps in 57%. Mapping could be used to guide 79% of operations. When no useful mapping data were obtained, patients had visually guided antiarrhythmic operations (17%) or conventional cardiac operations (4%). The most frequently performed antiarrhythmic procedures, alone or in combination, were endomyocardial resection (45%), cryothermal destruction (44%), and encircling procedures (20%). Operative mortality was 16%, including 6% from heart failure and 4% from ventricular tachycardia. Emergency operation (p = 0.002) and New York Heart Association heart failure class (p = 0.01) were independent preoperative risk factors for cardiac operative mortality in the 98 patients with coronary artery disease. At postoperative electrophysiologic study performed in 79 patients, ventricular tachycardia could not be induced in 75% of patients who had map-guided operations and 36% who had visually guided ones (p = 0.001). During follow-up of 23 +/- 21 months, results of postoperative electrophysiologic study predicted ventricular tachycardia recurrence. At 2 years the actuarial incidence of freedom from arrhythmia recurrence was 50% +/- 10% in patients with and 78% +/- 6% in patients without inducible ventricular tachycardia (p = 0.001); it was 71% +/- 5% in patients who had map-guided operations and 37% +/- 12% in patients who had visually guided ones (p = 0.004). Ventricular tachycardia recurrence was infrequent in survivors of map-guided operations; benefits of surgical treatment for ventricular tachycardia were limited by high operative mortality and frequent arrhythmia recurrence when no useful mapping data were obtained.

Actuarial Analysis↗
PubMed1985

The mechanisms of ventricular tachycardia in humans determined by intraoperative recording of the electrical activation sequence.

We recorded ventricular activation sequence during ventricular tachycardia in 76 patients who underwent surgical therapy of refractory ventricular tachycardia. Ventricular tachycardia arose from a discrete site (focal origination) in 28 patients (37%) or resulted from reentry around scar (macroreentry) in 22 patients (29%). The mechanism responsible for ventricular tachycardia was not discernable in the remaining 26 patients (34%), usually because of inadequacy of activation data. We conclude: (1) although focal originating of ventricular tachycardia is common, more frequently the mechanism is either macroreentry or uncertain, as assessed by conventional recording techniques; thus, a search for the "site of earliest activation" during ventricular tachycardia frequently may fail to direct rationally the operative procedure; (2) conventional techniques for intraoperative study of electrical activation during ventricular tachycardia are inadequate.

Cardiac Pacing, Artificial↗
PubMed1985

Independence of left ventricular pressure-volume ratio from preload in man early after coronary artery bypass graft surgery.

The response of the maximum value of the left ventricular pressure-volume ratio to preload augmentation by blood or plasma expanders was studied in 11 patients during the first 24 hr after coronary artery bypass graft surgery. Increasing the mean left atrial pressure from 10 to 15 and 20 mm Hg resulted in no change in the maximum pressure-volume ratio in the group as a whole. In certain individual patients, however, the maximum pressure-volume ratio changed with volume infusion, and these changes were accompanied by simultaneous changes in afterload. The observed changes in pressure-volume ratio were in the same direction as the changes in afterload (systolic pressure), suggesting a dependence of maximum pressure-volume ratio on afterload. These results show that the maximum pressure-volume ratio is independent of preload in the first 24 hr after coronary artery bypass graft surgery with the pericardium open; thus the maximum pressure-volume ratio is a useful index of postoperative left ventricular function when afterload is unchanged. However, because this ratio (a single-point assessment of the pressure-volume relationship) may not be a good estimate of Emax, we recommend a more complete determination of the locus of the "upper left corners" of the pressure-volume loops for measurement of Emax to provide a more accurate indicator of the myocardial contractile state.

Adult↗
PubMed1985

Effect of early postoperative volume loading on left ventricular systolic function (including left ventricular ejection fraction determined by myocardial marker) after myocardial revascularization.

The effects of early volume loading in terms of isovolumetric-phase and ejection-phase indexes of left ventricular systolic function were studied in 12 patients 5 hr after myocardial revascularization, with myocardial markers used to measure left ventricular volume directly and with simultaneous transmural left ventricular pressure measurements by micromanometers. Volume loading (increasing transmural left ventricular end-diastolic pressure from 11 +/- 4 to 15 +/- 5 mm Hg) induced a significant 14% increase in left ventricular end-diastolic volume index (LVEDVI), which was associated (as expected) with significant (p less than .005) augmentation of stroke work (+26%), left ventricular pressure-volume loop area (+35%), and stroke volume index (+22%) and with increments in left ventricular dP/dt and mean velocity of circumferential fiber shortening despite a simultaneous increase in left ventricular afterload. In contrast to previous radionuclide studies, however, left ventricular ejection fraction increased significantly (+9%) and the left ventricular end-systolic pressure-volume ratio did not fall. The relative change in ejection fraction was directly proportional to the increment in LVEDVI (r = .54, p = .03) and inversely related to the change in left ventricular end-systolic volume index (r = -.71, p = .0005). Patients who demonstrated a small or no increase in ejection fraction generally had a larger simultaneous increase in afterload, but one patient exhibited exhaustion of preload reserve. Ejection fraction, as an ejection-phase index of left ventricular performance, is highly dependent on afterload; therefore, interpretation of postoperative changes in ejection fraction must be undertaken only with strict caution.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Output↗
PubMed1985

Long-term hemodynamics following combined heart and lung transplantation in primates.

To assess the long-term hemodynamic consequences of combined heart and lung transplantation, we investigated six rhesus monkeys 2.6 to 4.6 years (mean 4.0) after operation. Total follow-up was 24.0 primate-years. Autotransplantation had been carried out in four animals and allotransplantation in two, and the hemodynamic results were compared with those in three normal monkeys of similar size. Each animal underwent simultaneous right and left heart catheterization and pulmonary arteriography. Hemodynamic measurements were made at three levels of inspired oxygen. Arterial oxygen tension was within normal limits in all animals, and pulmonary artery pressure and pulmonary vascular resistance index did not change significantly with changes in the levels of inspired oxygen. Indices of left ventricular systolic function were normal in all animals. Values for pulmonary artery pressure and pulmonary vascular resistance index were similar in the autograft and normal groups: in the allograft group, the average pressure was 30/17 mm Hg (mean 24) and the index was 5.6 units . m2--both levels significantly higher than normal (pressure was 16/10 mm Hg, mean 13, [p less than 0.001] and index was 2.5 units . m2 [p less than 0.02]). Pulmonary arteriography in the allograft group with the highest pulmonary vascular resistance index (6.1 units . m2) was compatible with pulmonary vascular disease. Pulmonary arteriograms in the remaining eight monkeys were normal. Prolonged survival following combined heart and lung transplantation is possible in primates. Autotransplantation (and probable persisting denervation of the cardiopulmonary axis) does not necessarily result in abnormal long-term hemodynamics. The elevation in pulmonary artery pressure and pulmonary vascular resistance index in the allograft group may be related to previous episodes of pulmonary rejection, infection, or drug reaction.

Animals↗
PubMed1984

The diuretic properties of dopamine in patients after open-heart operation.

Dopamine and dobutamine were administered to 12 patients who had undergone open cardiac operations. To eliminate the effects of variation in systemic blood flow upon renal function the drug infusion rates were adjusted to achieve equal cardiac outputs. Under conditions of equivalent systemic pressure and flow, dopamine (5.0 +/- 1 micrograms X kg-1 X min-1) and dobutamine (3.5 +/- 1.8 micrograms X kg-1 X min-1) had similar effects upon glomerular filtration rate (90 +/- 29 vs. 83 +/- 27 ml X min-1 X 1.73 m-2) and effective renal plasma flow (375 +/- 119 vs. 357 +/- 126 ml X min-1 X 1.73 m-2). However, dopamine administration resulted in a significantly greater diuresis (2.8 +/- 2.7 vs. 1.0 +/- 0.3 ml/min), natriuresis (0.32 +/- 0.39 vs. 0.07 +/- 0.10 mEq Na+/min), and kaliuresis (0.15 +/- 0.06 vs. 0.10 +/- 0.03 mEq K+/min) (P less than 0.05). In patients with modest depression of cardiac performance and renal vasoconstriction, dopamine's selective renal vasodilator effects were not evident. Furthermore, these data suggest that dopamine inhibits tubular solute reabsorption directly. Thus, the diuresis and natriuresis that frequently accompany dopamine administration may occur independently of any effects of dopamine upon renal blood flow.

Adult↗
PubMed1983

Vulnerability of patients with obstructive hypertrophic cardiomyopathy to ventricular arrhythmia induction in the operating room. Analysis of 17 patients.

To evaluate vulnerability to ventricular arrhythmia induction, programmed electrical stimulation was performed in the operating room in 17 consecutive patients undergoing myotomy-myectomy for obstructive hypertrophic cardiomyopathy (HC). A control group of 5 patients undergoing coronary artery bypass grafting with normal left ventricular function and no previous myocardial infarction also was tested. Of the 17 patients with HC, 14 had inducible sustained ventricular tachycardia (VT) or ventricular fibrillation (VF), 1 had inducible unsustained VT and the remaining 2 had less than 6 ventricular beats. In contrast, none of the 5 control patients had an inducible sustained ventricular arrhythmia, 1 had inducible unsustained VT, and the remaining 4 had less than 3 ventricular beats. The difference between the 2 groups with respect to induction of a sustained ventricular arrhythmia, unsustained VT or less than 6 ventricular beats was significant (p less than 0.001). It is concluded that patients with severe obstructive HC are unusually vulnerable to ventricular arrhythmia induction. This suggests that spontaneous ventricular tachyarrhythmias may be an important cause of sudden death in patients with HC.

Adolescent↗
PubMed1981

The renal effects of sodium nitroprusside in postoperative cardiac surgical patients.

Sodium nitroprusside (SNP) is frequently used to control hypertension and/or improve systemic blood flow following cardiac operations. Although SNP causes renal vasodilation when infused into isolated kidneys, the reported effects of SNP on renal vascular resistance and blood flow in intact animals and humans have varied. To define the effects of SNP in postoperative cardiac surgical patients, renal clearances and hemodynamics were measured in seven patients within 24 hours of coronary bypass grafting. Studies were delayed until patients were stabilized and had rewarmed following operation. Following baseline measurements (off SNP), SNP infusion was used to lower mean arterial pressure to 85 torr. Pulmonary wedge pressure was maintained by appropriate fluid therapy, and the measurements repeated 1 h later. SNP administration resulted in equivalent decreases in renal (-31 per cent), pulmonic (-29 per cent) and systemic (-33 percent) vascular resistance. Notwithstanding the decrease in arterial pressure (109 +/- 14 to 91 +/- 9 torr, P less than 0.01), renal blood flow increased by 20 per cent (653 +/- 193 to 792 +/- 210 ml . min-1 . 1.73 m-2, P less than 0.02), in direct proportion to the increase in cardiac index (2.5 +/- 0.4 to 3.0 +/- 0.3 1 . min-1 . m-2, P less than 0.01). Thus, in postoperative cardiac surgical patients, SNP administration can be expected to improve renal blood flow, so long as left atrial hypotension is avoided, and the decline in systemic arterial pressure is not excessive. The improvement in renal blood flow achievable with SNP may be critical for patients with severely depressed left ventricular function in whom severe depression of renal blood flow may occur as an antecedent to acute renal failure.

Acute Kidney Injury↗
PubMed1981

Effect of the intra-aortic balloon pump upon postoperative renal function in man.

Fifty-seven postoperative cardiac surgical patients receiving intra-aortic balloon pump (IABP) support were selected for detailed hemodynamic and renal function measurements on the basis of depressed cardiac and/or renal function. Eleven patients developed acute renal failure while receiving maximal IABP support and 10 during, or after withdrawal of IABP support. To define further the relationship between IABP support and renal function, 17 patients underwent simultaneous assessment of hemodynamic and renal function under varying conditions of IABP support. These studies, performed just before IABP withdrawal, demonstrated slight, clinically insignificant, improvement in hemodynamic and renal function with increased IABP support. Arterial pressure recordings, performed above and below the intra-aortic balloon in 8 patients, revealed no significant pressure gradient across the balloon whether single- or double-chambered. In addition, the balloon pulse waveform was always evident in the femoral artery. Importantly, the intra-aortic balloon did not interfere demonstrably with renal function, nor did it decrease renal perfusion pressure, in spite of its suprarenal position. Therefore, improvement in systemic perfusion from IABP support in the early postoperative period will result in improved renal perfusion.

Acute Kidney Injury↗
PubMed1980

Sequential pathophysiological changes characterizing the progression from renal dysfunction to acute renal failure following cardiac operation.

Sequential pathophysiological data were analyzed from 14 patients who exhibited similar severe depression of cardiac and renal function within 24 hours of cardiac operation. Seven patients exhibited postoperative renal dysfunction (defined by a minimum postoperative clearance of inulin [Cin] between 20 ml/min/1.73 m2 and one-half normal) and seven progressed from renal dysfunction to acute renal failure (ARF) (Cin less than or equal to ml/min/1.73 m2). In ARF patients depression of cardiac function was profound and persistent from postoperative days 1 to 7. Urine flow remained greater than 1 ml/min, and serum creatinine rose progressively. The Cin declined progressively during the first postoperative week. The ratio or urinary to plasma osmolality fell, and the fractional excretion of sodium (FENa) and potassium (FEK) increased substantially. By contrast, in renal dysfunction patients definite hemodynamic improvement occurred and renal function remained stable. Increased FENa in renal dysfunction was associated with hemodynamic improvement, weight loss, and stable fractional potassium excretion. These data provide unique documentation of the indices of hemodynamic and renal function associated with the progression to postoperative ARF. The central role of sustained profound depression of cardiac function in this progression appears to be the primary factor in the lethality of postoperative ARF.

Acute Kidney Injury↗
PubMed1977

Control of myocardial performance early after open-heart operations by vasodilator treatment.

The hemodynamic effects of vasodilator treatment (afterload reduction) with nitroprusside at a constant heart rate were studied in 24 patients early after aorta-coronary bypass grafting. In 12 patients, dose-response relationships were determined. Graded incremental infusions of nitroprusside produced progressive decreases in mean arterial pressure (MAP), right and left atrial pressures, and stroke work index. Stroke volume index and cardiac index rose significantly until MAP was reduced below the range of 80 to 90 mm. Hg, and then they fell to base-line levels owing to insufficient preload. In an additional 12 patients, MAP was reduced with nitroprusside to the range of 80 to 90 mm. Hg, and left atrial pressure was then restored to base-line levels during continued vasodilator administration. This sequence resulted in further augmentation of stroke volume index to a level higher than that produced by nitroprusside alone. We conclude from this investigation that nitroprusside is a clinically useful agent for primary or adjunctive therapy of mild-to-moderate low cardiac output states immediate postoperatively and that simultaneous regulation of left ventricular preload and after load during its administration is necessary in order to achieve maximal hemodynamic benefit.

Blood Pressure↗
PubMed1975

Action of drugs in patients early after cardiac surgery. I. Comparison of isoproterenol and dopamine.

Dopamine and isoproterenol were each administered in two different doses to 12 patients with coronary artery disease in the period immediately after open heart surgery. The two doses of dopamine resulted in respective increases in cardiac output of 23 and 43 percent and reductions in systemic vascular resistance of 23 and 32 percent; neither dose significantly altered heart rate. The two doses of isoproterenol caused respective increases of 23 and 37 percent in cardiac output and 18 and 28 percent in heart rate and reductions in systemic vascular resistance of 22 and 29 percent. We conclude that lack of chronotropic effect of dopamine as compared with isoproterenol may make the former the agent of choice in patients requiring inotropic agents for their care in the early period after cardiac surgery.

Blood Pressure↗