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Biomedical subjects

F A Crawford

Publications and source records attributed to F A Crawford.

At least 19 recordsLinked to original sources
PubMed1992

Effect of pulmonary resection on right ventricular function.

The effect of pulmonary resection on right ventricular (RV) performance and its possible contribution to morbidity or mortality remain unclear. Using thermodilution methods and a fast-response thermistor positioned in the pulmonary artery, it is now possible to measure RV end-diastolic volume and RV ejection fraction. Using this technique, RV performance during and after major pulmonary resection was studied in 15 patients. Significant RV dysfunction was demonstrated in the postoperative period. Right ventricular end-diastolic volume increased significantly on postoperative day 1 (177 +/- 9 mL) and postoperative day 2 (172 +/- 4 mL) versus early postoperatively (153 +/- 10 mL) (p less than 0.05). By postoperative day 2, RV ejection fraction was significantly decreased (0.36 +/- 0.03) from preoperative (0.45 +/- 0.02) and early postoperative (0.40 +/- 0.01) values (p less than 0.05). Although pulmonary artery pressures rose modestly in the postoperative period, and pulmonary vascular resistance increased by postoperative day 2, pulmonary vascular resistance remained significantly lower or unchanged from baseline values. We speculate that the etiology of the RV dysfunction after pulmonary resection may be multifactorial. Changes in RV afterload or alteration in RV contractility may be factors.

Adult↗
PubMed1992

Atrioventricular pacing in congenital heart disease.

We have attempted to optimize cardiac performance in patients with congenital heart disease requiring artificial pacing by using pacemakers capable of both sensing and pacing both the atrium and the ventricle (DDD). We reviewed our results with 88 patients receiving DDD devices to determine the safety and dependability of these devices in children. Age ranged from 1 hour to 25 years. Endocardial leads were used in 68 patients, whereas epicardial leads were used in 20 patients. Previous cardiac procedures had been done in 30 patients. There were nine deaths but none due to pacemaker malfunction. Endocardial leads functioned better than epicardial leads. Ninety-eight percent of patients with endocardial leads and 62% of patients with epicardial leads were maintained in the DDD mode. Complications were infrequent and all were corrected without long-term sequelae. The DDD mode may offer considerable benefits to children who require artificial pacing. Our data allow us to conclude that most children can be paced safely and dependably in the DDD mode.

Adolescent↗
PubMed1992

Retrograde versus antegrade cardioplegia: impact on right ventricular function.

Retrograde cardioplegia administered through the coronary sinus has several documented advantages over antegrade cardioplegia but has been thought to provide inadequate right ventricular myocardial protection. We prospectively compared the effects of retrograde and antegrade cardioplegia on right ventricular performance in patients undergoing myocardial revascularization. Two groups of similar age, extent of disease, and preoperative left ventricular ejection fraction received retrograde (n = 16) or antegrade (n = 14) crystalloid cardioplegia. A right ventricular rapid-response thermistor catheter, previously developed and validated in our institution, was used to measure right atrial pressure, pulmonary artery pressure, right ventricular ejection fraction, end-diastolic volume index, and stroke volume index before bypass (baseline) and at several intervals after bypass. There were no differences in cross-clamp time, heart rate, cardiac enzymes, inotrope requirements, or arrhythmias between the two groups. Right ventricular parameters were equivalent in both groups at all time intervals except 30 minutes after bypass, at which time right ventricular end-diastolic volume index was lower (80 +/- 6 versus 93 +/- 6 mL/m2; p less than 0.05) and right ventricular stroke volume index was higher (35 +/- 3 versus 29 +/- 2 mL/m2, p less than 0.05) in the retrograde group compared with the antegrade group, indicating better right ventricular function with retrograde cardioplegia early after bypass. In both groups, right ventricular end-diastolic volume index was higher than baseline (p less than 0.05) during the first 4 hours after bypass. No other important differences were found.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Myocardial Na+,K(+)-ATPase in tachycardia induced cardiomyopathy.

Na+,K(+)-ATPase is a major determinant of myocyte homeostasis and excitation-contraction. Cardiac glycosides such as digitalis and ouabain increase the inotropic state of the heart through the inhibition of Na+,K(+)-ATPase. While cardiac glycosides are commonly used in the setting of congestive heart failure, optimal therapy would depend upon an intact Na+,K(+)-ATPase system. Changes in Na+,K(+)-ATPase activity and glycoside receptor density with the development of cardiomyopathy have not been well defined. Accordingly, left ventricular (LV) function and Na+,K(+)-ATPase activity and glycoside binding were examined in 7 pigs with dilated cardiomyopathy and in 7 controls. Dilated cardiomyopathy was produced by pacing induced supraventricular tachycardia (SVT) for 3 weeks at 240 bpm. Left ventricular function was examined by simultaneous echocardiography and catheterization. Left ventricular fractional shortening significantly decreased with SVT (34 +/- 2 vs. 10 +/- 2%, P less than 0.05) and LV diastolic dimension and pressure significantly increased (3.8 +/- 0.3 vs. 5.1 +/- 0.4 cm, and 8 +/- 2 vs. 27 +/- 2 mmHg, respectively, P less than 0.05) as compared to controls. Na+,K(+)-ATPase activity was assayed as potassium dependent p-nitrophenol-phosphatase activity. Glycoside receptor density (Bmax) and affinity (KD) was determined using [3H]-ouabain binding assays. Na+,K(+)-ATPase activity, Bmax, and KD all significantly fell from control values with SVT induced cardiomyopathy (0.64 +/- 0.06 vs. 0.45 +/- 0.12 micrograms pNP/mg/h, 5.5 +/- 0.4 vs. 1.9 +/- 0.4 pmol/mg, and 15 +/- 3 vs. 9 +/- 3 nM, respectively, P less than 0.05). The distribution of Na+,K(+)-ATPase in LV sections taken from control and SVT hearts were examined using immunohistochemical techniques. A patchy distribution of Na+,K(+)-ATPase along the sarcolemma in SVT sections was observed as opposed to a more uniform distribution in control myocytes. There was no observable change in the relative content and distribution of the Na+,K(+)-ATPase isoforms alpha 2 and alpha 3 in the SVT sections as compared to controls. In an additional set of experiments, changes in LV as well as isolated myocyte responsiveness to ouabain were examined. Left ventricular fractional shortening and peak dP/dt were measured following administration of 20-60 micrograms/Kg of ouabain in control (n = 3) and SVT (n = 3) pigs. In the control group, 40 micrograms/Kg caused a 25% in LV fractional shortening and a 60% increase in peak dP/dt from baseline. Cumulative doses of 60 micrograms/Kg in the control pigs resulted in over a 75% increase in peak dP/dt from baseline values.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Aortic valve resistance as an adjunct to the Gorlin formula in assessing the severity of aortic stenosis in symptomatic patients.

OBJECTIVES: This study was conducted to determine the utility of aortic valve resistance in assessing the severity of aortic stenosis. BACKGROUND: Assessment of the severity of aortic stenosis has traditionally employed hemodynamic data and the Gorlin formula to calculate the area of the aortic valve. Recently, flow dependence of the Gorlin formula has been identified and the accuracy of the formula challenged. Aortic valve resistance, the quotient of gradient and cardiac output, has been advanced as potentially useful in assessing the severity of valve stenosis. METHODS: We studied 48 symptomatic patients with an initial diagnosis of severe aortic stenosis based on a calculated aortic valve area of less than or equal to 0.8 cm2 by the Gorlin formula. Forty of these patients (Group I) were confirmed to have severe aortic stenosis, whereas 8 (Group II) were subsequently proved not to have severe aortic stenosis. The 18 patients in Group I with a valve area of 0.6 to 0.8 cm2 (Group IA) were directly compared with Group II patients who had a similar valve area. RESULTS: Aortic valve area was nearly identical in Group IA and Group II patients (0.69 +/- 0.05 and 0.71 +/- 0.06 cm2, respectively, p = NS). However, aortic valve resistance was much less in Group II patients (212 +/- 6 vs. 316 +/- 11 dynes.s.cm-5, p less than 0.0001). In this small cohort, aortic valve resistance achieved nearly complete separation of patients in Groups IA and II. CONCLUSIONS: In some patients with relatively mild aortic stenosis, the calculated valve area may indicate that the stenosis is severe. The use of aortic valve resistance in conjunction with the Gorlin formula helps separate patients with truly severe aortic stenosis from those with milder disease.

Aged↗
PubMed1992

Effect of chronic supraventricular tachycardia on left ventricular function and structure in newborn pigs.

OBJECTIVES: The purpose of this study was to examine the effects of supraventricular pacing tachycardia on left ventricular function and myocardial structure in newborn, immature pigs and to determine whether immature pigs respond to supraventricular tachycardia differently from adults. BACKGROUND: Previous studies have shown that supraventricular tachycardia causes dilated cardiomyopathy in adult animals; however, in humans, supraventricular tachycardia-induced congestive heart failure occurs most frequently in children and newborns. Because some clinical diseases may cause myocardial failure in adults but rarely do so in children, it was hypothesized that the effects of supraventricular tachycardia in newborns may be different from those in adults. METHODS: In two groups of newborn swine (3 weeks of age), left ventricular volume, mass and function were assessed with simultaneous echocardiography and cardiac catheterization and myocardial structure was examined with light and electron microscopy. Six piglets underwent 3 weeks of left atrial pacing tachycardia (240 beats/min) and six littermates served as a control group. Both groups were followed up for 3 weeks. RESULTS: At the end of the protocol, left ventricular dimensions increased in the piglets with supraventricular tachycardia compared with values in the control group, but there were no differences in left ventricular mass. Systolic function, assessed by fractional shortening, peak ejection rate and maximal rate of pressure development, was decreased in the group with supraventricular tachycardia. The fractional shortening-end-systolic stress relation in the piglets with supraventricular tachycardia decreased below normal values. Left ventricular diastolic function assessed by the relaxation time constant was prolonged, the peak filling rate was decreased and left ventricular stiffness was increased in the supraventricular tachycardia group. The morphologic data demonstrated that supraventricular tachycardia did not change total myocyte volume but did decrease total myofibrillar volume. CONCLUSIONS: Supraventricular tachycardia caused dilated cardiomyopathy in immature pigs. These changes in left ventricular function were associated with a decrease in cellular contractile proteins. Thus, the effects of supraventricular tachycardia on left ventricular function and structure in immature animals were comparable to previous findings in mature animals.

Age Factors↗
PubMed1992

Surgical management of dysrhythmias in infants and small children.

Surgery for cardiac dysrhythmias is infrequently reported in infants and children as compared with adults. This report reviews 55 infants and small children (age, less than or equal to 5 years) operated on during the interval July 1, 1984 to December 31, 1991 for Wolff-Parkinson-White Syndrome (41), atrioventricular node reentry (two), atrial automatic tachycardia (two), and ventricular tachycardia (nine). Ages ranged from 3 weeks to 71 (mean, 29) months. Associated congenital heart defects were present in five (10%). Indications for surgery included failure of medical therapy, life-threatening dysrhythmias, and more recently, failure of catheter ablation. There were no hospital or late deaths. One patient sustained perioperative central nervous system injury. Surgery was successful in 52 of 55 (94.5%) (Wolff-Parkinson-White, 38/41 (93%); atrioventricular node reentry, 2/2 (100%); atrial automatic tachycardia, 3/3 (100%); ventricular tachycardia, 9/9 (100%). Ventricular function returned to normal in all 12 patients in whom it was abnormal before operation. Thus, surgical ablation is highly successful in the management of various forms of refractory or life-threatening dysrhythmias in infants and small children. Catheter ablation techniques require significant fluoroscopic time, are more difficult in infants, and as yet do not have adequate long-term follow-up. Accordingly, surgery may continue to play a role in this particular group of patients.

Arrhythmias, Cardiac↗
PubMed1992

Right atrial diverticulum presenting as Wolff-Parkinson-White syndrome.

A 7-year-old male presenting with Wolff-Parkinson-White syndrome and tachycardia was suspected by echocardiographic and magnetic resonance imaging evaluation to have an associated pericardial cyst anterior to the right atrium and ventricle. Electrophysiological evaluation demonstrated short antegrade and retrograde accessory connection refractory periods, with inducible orthodromic atrioventricular reentrant tachycardia. Surgical observation revealed a rare congenital right atrial diverticulum bridging the anterior right atrioventricular groove, with the functional accessory connection lateralized to the medial aspect of this structure. Endocardial and epicardial incisions and cryolesions placed along the anterior right atrioventricular groove initially appeared successful, but preexcitation recurred within 4 weeks postoperatively.

Cardiac Pacing, Artificial↗
PubMed1992

Changes in myocardial blood flow during development of and recovery from tachycardia-induced cardiomyopathy.

BACKGROUND: Chronic supraventricular tachycardia (SVT) causes a dilated cardiomyopathy and myocyte injury. Termination of SVT improves left ventricular (LV) function but is associated with LV hypertrophy. Changes in myocardial blood flow (MBF) that may accompany the development of and recovery from SVT cardiomyopathy might have a significant effect on LV function and myocyte structure. The goal of this study was to relate changes in LV function, myocyte composition, and coronary vascular structure to changes in MBF with the development and recovery of SVT cardiomyopathy. METHODS AND RESULTS: LV function and MBF were measured in three groups of conscious pigs: sham control (control; n = 8), after 3 weeks of atrial pacing (SVT, 240 beats per minute; n = 8), and after a 4-week recovery from SVT (post-SVT; n = 8) by echocardiography catheterization and microspheres. Measurements were made under three states: 1) at rest with a basal heart rate, 2) rapid atrial pacing (240 beats per minute), and 3) during adenosine infusion (1.5 mumol/l.kg-1.min-1) without pacing. LV myocyte, capillary, and arteriole morphometric studies were performed in five additional pigs from each group using histochemistry and electron microscopy. LV fractional shortening was lower and left atrial pressure was significantly higher in the SVT group compared with control at rest, during pacing, and with adenosine (p less than 0.05). In the post-SVT group, fractional shortening returned to control values at rest and with adenosine, but fell from control values with pacing (p less than 0.05). Left atrial pressure fell in the post-SVT but remained significantly higher than control (p less than 0.05). LV/body weight ratio was significantly increased in the post-SVT group (p less than 0.05). In all states, SVT LVMBF was significantly reduced from control values (rest, 0.8 +/- 0.3 versus 1.6 +/- 0.3 ml-min-1.g-1; pacing, 1.2 +/- 0.2 versus 3.1 +/- 0.3 ml.min-1.g-1; adenosine, 1.4 +/- 0.3 versus 4.4 +/- 0.4 ml.min-1.g-1, respectively, p less than 0.05). In the post-SVT group, LVMBF was similar to control at rest (1.3 +/- 0.2 ml.min-1.g-1) but was significantly lower than control with pacing and adenosine (2.0 +/- 0.4 and 2.5 +/- 0.5 ml.min-1.g-1, respectively, p less than 0.05). Myofibrillar content fell significantly with SVT compared with control (42 +/- 5 versus 61 +/- 3%, p less than 0.05) and returned to control values in the post-SVT group (64 +/- 3%). Capillary density remained unchanged in the SVT and post-SVT groups, but capillary luminal diameter decreased and arteriole diameter increased in the SVT group (p less than 0.05). CONCLUSIONS: The LV dysfunction and myocyte injury with SVT cardiomyopathy were associated with reduced MBF. Early recovery from SVT cardiomyopathy resulted in hypertrophy with normal MBF at rest, but significantly reduced coronary reserve.

Adenosine↗
PubMed1992

Relation between ventricular and myocyte function with tachycardia-induced cardiomyopathy.

Chronic supraventricular tachycardia (SVT) causes left ventricular (LV) dilatation and dysfunction. Changes in myocyte function and structure may be important factors in the development of SVT cardiomyopathy. Accordingly, LV function and isolated myocyte structure and function were examined in six pigs with pacing-induced SVT cardiomyopathy (3 weeks at 240 beats per minute) and six control pigs. LV function was examined by simultaneous echocardiography and catheterization, and isolated myocyte function was studied using computer-assisted video microscopy. Indexes of isolated myocyte contractile performance were examined in the unloaded, unattached state (31 control and 24 SVT cells) and after attachment to a basement membrane substrate (65 control and 45 SVT cells). LV fractional shortening and peak +dP/dt significantly decreased in SVT cells compared with control cells (12 +/- 2% versus 28 +/- 2%, and 842 +/- 61 versus 1,216 +/- 119 mm Hg/sec, respectively; p less than 0.05). Isolated myocyte percent shortening and normalized peak velocity of shortening of SVT myocytes adherent to a basement membrane were significantly lower than attached control myocytes (1.2 +/- 0.2% versus 4.3 +/- 0.3%, and 15 +/- 2 versus 37 +/- 5% resting cell length/sec, respectively; p less than 0.05). Similarly, in the unattached state, the extent and velocity of shortening of SVT myocytes were reduced by over 50% from control values. Contractile properties of attached and unattached cardiocytes were also examined in the presence of 2-8 mM extracellular Ca2+. For both attached and unattached SVT myocytes, responsiveness to increases in extracellular Ca2+ were significantly blunted from control values. Ultrastructural examination of SVT myocytes revealed that the percent volume of myofibrils within isolated myocytes was reduced from control values (46 +/- 7% versus 65 +/- 2%, p less than 0.05). In summary, SVT cardiomyopathy is probably due to a primary defect in isolated myocyte contractile performance. The reduced contractile function of SVT cardiomyopathic myocytes was associated with abnormalities in cytoarchitecture and Ca2+ responsiveness.

Animals↗
PubMed1992

Effects of chronic tachycardia-induced cardiomyopathy on the beta-adrenergic receptor system.

Chronic supraventricular (or ventricular) tachycardia causes a dilated cardiomyopathy. Effective treatment requires ablation of the tachycardia using antiarrhythmic agents, cryoablation, electroablation, or surgical interruption/excision. However, the underlying pathophysiologic mechanisms responsible for the development of supraventricular tachycardia-induced cardiomyopathy have not been fully identified. We hypothesized that chronic supraventricular tachycardia is associated with significant changes in the beta-adrenergic system that may have implications for the pathophysiology and treatment of supraventricular tachycardia-induced cardiomyopathy. Accordingly, we examined the relationship between left ventricular function, plasma norepinephrine level, beta-receptor number and affinity, and response to a beta-agonist (isoproterenol) infusion in eight control pigs and eight pigs subjected to supraventricular pacing-induced tachycardia (240 beats/min for 3 weeks). Left ventricular function was measured using simultaneous echocardiography and catheterization. Left ventricular end-diastolic dimension and pressure increased in pigs with supraventricular tachycardia (5.1 +/- 0.4 cm and 27 +/- 2 mm Hg) versus control pigs (3.8 +/- 0.3 cm and 8 +/- 2 mm Hg), p < 0.05. Left ventricular fractional shortening decreased in supraventricular tachycardia (10 +/- 1%) versus control pigs (34 +/- 1%), p < 0.05. In addition, in the pigs with supraventricular tachycardia the fractional shortening versus left ventricular end-systolic stress relationship fell below the control relationship. Plasma norepinephrine level (measured by high-performance liquid chromatography) increased in pigs with supraventricular tachycardia (3592 +/- 1606 pg/ml plasma) versus control pigs (323 +/- 74 pg/ml plasma), p < 0.05. beta-Receptor number and affinity (measured by [3H]dihydroalprenolol binding) did not change in supraventricular tachycardia (98.6 +/- 11.5 fmol/mg protein and 7.2 +/- 1.1 nmol) versus control pigs (99.1 +/- 9.4 fmol/mg protein and 6.8 +/- 0.5 nmol). The response to isoproterenol infusion (10 micrograms/kg) in supraventricular tachycardia was blunted: the absolute increase in left ventricular peak (+)dP/dt was reduced in supraventricular tachycardia (833 +/- 233 mm Hg/sec) versus control pigs (2180 +/- 139 mm Hg/sec), p < 0.05. Chronic supraventricular tachycardia caused a decreased contractile state, increased plasma norepinephrine level, and caused no change in beta-receptor number or affinity; however, the response to beta-agonist infusion was blunted. These results suggest that chronic supraventricular tachycardia is associated with uncoupling of the beta-receptor from subsequent intracellular components of the beta-adrenergic system. Therefore medical management of chronic supraventricular tachycardia-induced cardiomyopathy before and immediately after definitive ablation may require use of pharmacologic agents whose actions do not depend on an intact beta-adrenergic pathway.

Animals↗
PubMed1991

In vitro validation of a right ventricular thermodilution ejection fraction system.

Right ventricular ejection fraction (RVEF) is used clinically as an index of right ventricular (RV) pump function. Clinical measurements of RVEF are complicated by the need for complex imaging equipment to compute RV volumes. Recently, the use of thermodilution (TD) methods have been suggested as a simplified means to measure RVEF (RVEFTD) in patients using rapid response thermistors. Validation, however, by comparison of RVEFTD and other methods in vivo, is difficult. Accordingly, thermodilution derived EF measurements (EFTD) were compared to known values using an in vitro system, with known ejection fractions (EF) set from 17-78% and stroke rates varying independently from 50-100 strokes/min. EFTD was computed by fitting the downslope of the TD curve to a monoexponential function and computing the time constant of thermal decay. A significant correlation existed between EFTD and actual EF over the entire study (r = 0.96, p less than 0.001). Bias analysis showed that the points were within a 95% confidence interval of +/- 12%. Multivariate analysis showed that stroke rate did not significantly affect TD measurements (r = 0.03, p greater than 0.7). This study demonstrates that TD accurately predicts EF using an in vitro system and appears to be independent of stroke rate. Thus, TD methods may provide an accurate, simple and reliable means to serially measure RVEF in the clinical setting.

Algorithms↗
PubMed1991

Right ventricular pump dysfunction with acute experimental septic shock.

Right ventricular (RV) function has been poorly characterized at the onset of acute bacterial septic shock. Using a volumetric thermodilution catheter, previously validated in our laboratory, we serially measured RV function in a porcine model of acute septic shock. Six pigs (21.3 +/- 0.9 kg) were instrumented and Pseudomonas aeruginosa (3.4 x 10(8) cfu/ml, 0.3 ml/20 kg/min) was infused. RV ejection fraction, RV volumes, cardiac output, arterial pressure, central venous pressure, and pulmonary arterial pressure were measured at baseline and at 30, 60, 120, and 240 min after starting the bacterial infusion. RV ejection fraction and stroke volume were decreased at 30 min compared to baseline (21 +/- 5 vs 43 +/- 5% and 14 +/- 3 vs 23 +/- 3 ml, respectively; P less than 0.05) and remained depressed throughout the experiment. Mean arterial pressure was significantly reduced at 60, 120, and 240 min compared to baseline (P less than 0.05). There was a significant increase in pulmonary vascular resistance (1771 +/- 493 vs 301 +/- 99 dyn-sec-cm-5 at 30 min; P less than 0.05) and RV stroke work (5.7 +/- 1.1 vs 2.3 +/- 0.3 gm-m/beat at 30 min; P less than 0.05) while no significant change in RV end-diastolic volume or central venous pressure was observed. Thus, a decrease in RV pump performance was associated with an increase in afterload and no change in preload. These results suggest that severe RV pump dysfunction occurs early in acute septic shock. This was manifested by significant reductions in RV ejection fraction and increased in stroke work.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Ventricular function and Na+,K(+)-ATPase activity and distribution with chronic supraventricular tachycardia.

STUDY OBJECTIVE: The molecular and cellular mechanisms responsible for the dilated cardiomyopathy associated with chronic supraventricular tachycardia are not well understood. The purpose of this study was to examine Na+,K(+)-ATPase activity and distribution in a pacing induced model of dilated cardiomyopathy. DESIGN: Left ventricular function and Na+,K(+)-ATPase activity and distribution were examined in two groups of pigs: (1) atrially paced for 3 weeks (supraventricular tachycardia, 240 beats.min-1); (2) sham operated controls. SUBJECTS: 10 Yorkshire male swine (23-25 kg) were randomly assigned to the control group or the supraventricular tachycardia group. MEASUREMENTS AND MAIN RESULTS: Left ventricular function was examined using simultaneous pressure echocardiography. Na+,K(+)-ATPase activity was determined in tissue homogenates by measuring the rate of p-nitrophenol-phosphate (pNPP) hydrolysis. Changes in content and distribution of Na+,K(+)-ATPase were examined immuno-histochemically in tissue sections. Left ventricular fractional shortening decreased significantly with supraventricular tachycardia as compared to controls, at 15 (SEM 3)% v 31(3)%, respectively p less than 0.05. Supraventricular tachycardia resulted in a significant increase in end diastolic dimension [5.0(0.3) cm v 3.5(0.2) cm, respectively p less than 0.05] and pressure [22(4)mm Hg v 6(2)mm Hg, respectively p less than 0.05]. Maximal Na+,K(+)-ATPase activity (microgram pNPP.mg-1 protein.h-1) was significantly lower with supraventricular tachycardia than in controls, at 0.45(0.12) v 0.64(0.06), respectively p less than 0.05. In the presence of 7 microM digitalis, Na+,K(+)-ATPase activity was inhibited by 68% in control and by 45% in supraventricular tachycardia homogenates (p less than 0.05). In control sections all left ventricular myocytes showed a uniform immunostaining pattern along the sarcolemma for Na+,K(+)-ATPase, whereas a focal loss of staining was observed in myocytes from the supraventricular tachycardia group. CONCLUSIONS: The congestive cardiomyopathy produced by supraventricular tachycardia was associated with a reduction in sarcolemmal Na+,K(+)-ATPase activity and changes in enzyme distribution. The findings also suggest a reduction in digitalis sensitivity with chronic supraventricular tachycardia. These alterations in Na+,K(+)-ATPase activity may be one potential mechanism responsible for the depressed left ventricular function associated with chronic supraventricular tachycardia.

Animals↗
PubMed1991

Placement considerations for measuring thermodilution right ventricular ejection fractions.

BACKGROUND AND METHODS: Clinical examination of right ventricular (RV) performance has been hampered by the inability to measure easily RV volumes and ejection fraction. This study was performed to examine the effects of catheter position on thermodilution RVEF measurements. Six pigs (80 to 100 kg) were instrumented with an RV thermodilution catheter in the pulmonary artery, an injectate catheter in the right atrium, an atrial pacing electrode, and a systemic arterial catheter. RVEF measurements were determined using thermodilution in two ways: a) with incremental increases in pulmonary valve to thermistor distance; and b) with incremental increases in injectate port to tricuspid valve distance. These measurements were obtained at a paced rate of 102 +/- 2 beats/min and then repeated with pacing-induced tachycardia (140 beats/min). RESULTS: There was no significant difference in thermodilution RVEF measurements with the thermistor positioned 0 to 10 cm from the pulmonary valve at either heart rate. A significant reduction in RVEF occurred with the injection port located 5 to 7 cm proximal to the tricuspid valve, with this decrease becoming more pronounced during tachycardia. CONCLUSIONS: These results demonstrate that RVEF measurements can be reliably obtained using thermodilution. In these large hearts, thermodilution RVEF measurements appear to be independent of thermistor position within the pulmonary artery. However, large distances from injectate port to tricuspid valve reduced RVEF measurements.

Animals↗
PubMed1991

Tachycardia-induced cardiomyopathy: effects on blood flow and capillary structure.

Chronic supraventricular tachycardia (SVT) causes a dilated cardiomyopathy. A potential factor contributing to the development of SVT-induced cardiomyopathy is abnormal myocardial blood flow (MBF). The purpose of this study was to relate changes in left ventricular (LV) function, MBF, and capillary structure with the development of SVT-induced cardiomyopathy. LV function and MBF were measured in two groups of conscious pigs: sham control (CON; n = 8) and after 3 wk of atrial pacing (SVT; 240 beats/min; n = 8) using echocardiography-catheterization and microspheres. Measurements were made under three states: 1) at rest with a basal heart rate, 2) during rapid atrial pacing (240 beats/min), and 3) during adenosine infusion (1.5 microM.kg-1.min-1) without pacing. LV capillary density, diameter, wall thickness, and capillary-myocyte distance were measured in four additional pigs from each group. LV fractional shortening was lower, and left atrial pressure was significantly higher in the SVT group compared with CON at rest, during pacing, and with adenosine (P less than 0.05). In the CON group, average LV-MBF at rest was 2.0 +/- 0.2 ml.min-1.g-1, increased with pacing to 3.0 +/- 0.2 ml.min-1.g-1 (P less than 0.05), and increased further with adenosine to 4.1 +/- 0.3 ml.min-1.g-1 (P less than 0.05). In all states, SVT LV-MBF was significantly reduced vs. CON (P less than 0.05); SVT LV-MBF was 0.8 +/- 0.2 ml.min-1.g-1 at rest, increased to 1.3 +/- 0.3 ml.min-1.g-1 with rapid pacing (P less than 0.05), and remained unchanged during adenosine (1.3 +/- 0.4 ml.min-1.g-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗