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Biomedical subjects

C T Ting

Publications and source records attributed to C T Ting.

At least 73 records · Page 4Linked to original sources
PubMed1993

Diastolic compliance of hypertrophied ventricle is not acutely altered by pharmacologic agents influencing active processes.

OBJECTIVE: To test, by studying the acute effects of drugs that influence active processes, the hypothesis that in humans with marked ventricular hypertrophy, reduced chamber compliance is primarily caused by passive structural changes. DESIGN: An uncontrolled (before-after) study. SETTING: University Medical Center. PATIENTS: Fourteen patients with ventricular hypertrophy (19 +/- 4.5-mm diastolic-wall thickness) and normal resting systolic function were studied while they had invasive cardiac catheterization. INTERVENTION: Intravenous beta-blocker (esmolol) or calcium channel blocker (verapamil) or both. MEASUREMENTS: Left ventricular function was determined by pressure-volume relations. Volume was measured using conductance catheter, providing a continuous voltage signal proportional to chamber volume. Pressure was measured by micromanometer. Cardiac-specific assessment of change in chamber contractility and diastolic compliance due to each drug was determined. RESULTS: Both drugs lowered contractility by approximately 30% (P < 0.01). Esmolol slowed relaxation and reduced early peak filling rate, whereas verapamil delayed the time to peak filling (all P < 0.05). In contrast to the effects of both drugs on active contraction and early diastole, late-diastolic compliance was unaltered, and end-diastolic pressure-volume relations were almost identical. CONCLUSION: Neither beta-receptor nor calcium channel blockade acutely alters left ventricular compliance despite substantial active effects manifest in systole and early diastole. This supports the notion that chamber compliance is principally determined by passive structural elements in the heart rather than by active processes.

Adrenergic beta-Antagonists↗
PubMed1993

Recurrent conduction in accessory pathway and possible new arrhythmias after radiofrequency catheter ablation.

Radiofrequency catheter ablation was performed in 142 patients with 166 accessory pathways. One hundred thirty-six patients with 160 accessory pathways underwent successful ablation in the first ablation session. Serial follow-up electrophysiologic studies were performed immediately (30 minutes), early (5 to 7 days), and late (3 to 6 months) after successful ablation to determine the recurrent accessory pathway conduction and possible new arrhythmias. After a minimum follow-up period of 6 months (mean, 14 +/- 3 months), accessory pathway conduction recurred in 13 patients (9.6%), with recurrent tachycardia in three patients (2.2%). Five of the recurrent accessory pathways had decremental conduction properties. Incidence of recurrent accessory pathway conduction was similar in different accessory pathway locations (6.4% to 9.0%). Patients with concealed accessory pathways (12.2 vs 2.9%; p < 0.05), and patients without accessory pathway potentials in the ablation site (15.5% vs 2.2%; p < 0.05) had a higher recurrence rate. Patients without tachycardia in the late electrophysiologic study did not have recurrent tachycardia during follow-up. New arrhythmias, including atrial and ventricular arrhythmias, which were detected by 24-hour Holter monitoring, were apparent only on the first day after ablation. The findings indicate that the overall incidence of recurrent accessory pathway conduction was low and that possible new arrhythmias were rare in the late follow-up period.

Adult↗
PubMed1993

Arrhythmogenicity of catheter ablation in supraventricular tachycardia.

To evaluate arrhythmogenicity in patients who receive a modified direct-current (DC) shock ablation (distal pair of electrodes connected in common as the cathode) or radiofrequency (RF) ablation of supraventricular tachycardia, a prospective study was performed with signal-averaged ECG, 24-hour Holter monitoring, electrophysiologic study (EPS) for ventricular tachycardia (VT), and treadmill exercise test. Sixty-nine consecutive patients with documented paroxysmal supraventricular tachycardia were included. Twenty-eight patients proved to have atrioventricular nodal reentrant tachycardia, and 41 patients had atrioventricular reciprocating tachycardia that involved accessory atrioventricular pathways. The first 34 patients received DC shock ablation and the other 35 patients received RF ablation. Signal-averaged ECG, Holter monitoring, and EPS for VT were performed before ablation, immediately after ablation, then 1 week, 2 weeks (Holter monitoring), 1 month (except EPS), and 3 months after ablation. Treadmill exercise testing was performed before ablation, and at 1 week and 3 months after ablation. The root mean square, low-amplitude signal and QRS duration of signal-averaged ECG disclosed no significant change after either DC or RF ablation up to 3 months. Late potential developed in only one patient in the DC shock group and it was considered to be innocuous because neither VT nor ventricular fibrillation was noted or induced. Increases in the number of ventricular premature contractions and in short-run VT were detected by Holter monitoring in the first week after either mode of ablation (p < 0.001 for the DC shock group; p < 0.05 for the RF group), which were greater (p < 0.05) and lasted longer in the DC shock group than in the RF group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Selective radiofrequency catheter ablation of fast and slow pathways in 100 patients with atrioventricular nodal reentrant tachycardia.

One hundred patients received selective radiofrequency ablation of retrograde fast pathway (32 patients, group I) or slow pathway (68 patients, group II) to treat drug-refractory atrioventricular nodal reentrant tachycardia. In group I, a mean of 6 +/- 3 radiofrequency pulses eliminated the retrograde fast pathway. Thirty patients were free of symptoms and were not receiving antiarrhythmic drugs; two patients had accidental atrioventricular block. One patient had recurrent tachycardia and received a repeated ablation (slow pathway ablation). In group II, a mean of 9 +/- 4 radiofrequency pulses eliminated the slow pathway in 68 patients. All patients were free of symptoms and were not receiving antiarrhythmic drugs. One patient had recurrent tachycardia and received a repeated ablation. Serial follow-up electrophysiologic studies (immediate [20 to 30 minutes], early [5 to 7 days], and late [3 to 6 months]) showed that selective ablation of retrograde fast pathway was associated with nonspecific injury on the antegrade fast pathway (increase of AH interval) without effects on the slow pathway. Selective ablation of slow pathway was associated with nonspecific injury on the retrograde fast pathway in 15 patients (22%), but the antegrade fast pathway conduction parameters did not change significantly. Thus retrograde and antegrade fast pathway may be anatomically similar or have different sensitivities to radiofrequency energy, and slow pathway may be anatomically distinct from fast pathway. We conclude that (1) selective radiofrequency ablation of retrograde fast or slow pathway could cure atrioventricular nodal reentrant tachycardia with a high success rate (98%) and a low recurrence rate (2%) during a follow-up period of 6 to 18 months, but fast pathway ablation was associated with accidental atrioventricular block (5%), and (2) serial follow-up electrophysiologic studies elucidated the possible mechanisms of cure in atrioventricular nodal reentrant tachycardia.

Adolescent↗
PubMed1993

Reappraisal of radiofrequency ablation of multiple accessory pathways.

Complete electrophysiologic study and radiofrequency ablation were performed in 145 consecutive patients with Wolff-Parkinson-White syndrome. Presence of multiple accessory atrioventricular pathways was documented in 20 patients (13.8%); 17 had two, two had three, and one had four accessory pathways. Location of accessory pathways was posteroseptal in 18, left free wall in 15, right free wall in nine, and right midseptal in two. Of the 44 pathways, 36 were found during baseline electrophysiologic study and eight were found after successful ablation of the initially attempted pathways. After delivery 20 +/- 23 pulses (per patient) of radiofrequency energy (37 +/- 6 W, 70 +/- 30 seconds), 43 accessory pathways were ablated successfully without complications. Duration of the procedure (4.5 +/- 1.7 vs 3.7 +/- 1.6 hours, p < 0.05) and radiation exposure time (53 +/- 30 vs 38 +/- 18 minutes, p < 0.05) were longer in patients with multiple pathways, whereas the success rate (95% vs 95%, p > 0.05) and incidence of recurrent conduction (11% vs 11%, p > 0.05) were similar in patients with single or multiple accessory pathways. These findings confirmed that multiple accessory pathways were common in patients with Wolff-Parkinson-White syndrome, and these pathways could be ablated successfully by radiofrequency energy with a success rate comparable to that of a single accessory pathway.

Adult↗
PubMed1993

Diminished contractile response to increased heart rate in intact human left ventricular hypertrophy. Systolic versus diastolic determinants.

BACKGROUND: Experimental studies indicate that in addition to diastolic dysfunction, hypertrophied myocardium can display depressed contractile responses, particularly at rapid heart rates, compounding reserve limitations. This study tests whether such abnormalities exist in intact human subjects at physiological paced rates and, if so, whether they are linked to simultaneous rate-dependent deterioration in diastolic function. METHODS AND RESULTS: Ten subjects with left ventricular hypertrophy (LVH) and 8 normal control subjects were studied. Most LVH patients presented with dyspnea and/or pulmonary edema and had concentric hypertrophy. Since rapid pacing simultaneously alters cardiac filling volumes and pressures, pressure-volume relation analysis was used to better define changes in contractile response. Patients were instrumented with a conductance catheter and micromanometer for pressure-volume data recording and a balloon occluder at the right atrial-inferior vena caval junction to vary filling and thus generate function relations. Data were obtained at baseline and at three atrial pacing rates (100, 120, 150 min-1). In addition, single-beat force-interval data were used to indirectly examine calcium cycling kinetics. LVH subjects demonstrated baseline diastolic abnormalities, including prolonged relaxation, elevated end-diastolic pressure, and reduced chamber compliance. However, systolic function was similar to that in control subjects. With rapid pacing, normal subjects displayed a positive contractile response, whereas this was markedly diminished in LVH subjects. With abrupt termination of pacing and return to slower sinus rhythm, LVH subjects displayed greater initial potentiation followed by a more rapid decline than control subjects, suggesting abnormalities of calcium handling. Despite contractile abnormalities, diastolic function did not further deteriorate with rapid pacing and thus did not appear to be tightly linked to the systolic changes. CONCLUSIONS: Pacing stress in intact human LVH can result in systolic impairment superimposed on preexisting but not worsened diastolic dysfunction. Abnormal calcium handling probably contributes prominently to this response.

Calcium↗
PubMed1993

Validation of a method for noninvasive measurement of central arterial pressure.

The goal of this study was to validate a newly improved noninvasive method for calibrated measurement of the ascending portion of the central arterial pressure wave in humans. Noninvasive pressure waveforms were generated by measuring the time delay between the R wave of the electrocardiogram and onset of brachial artery flow (by Doppler) during computer-controlled upper arm cuff deflation. This delay shortens with falling cuff pressure (becoming near constant at and below diastolic pressure), so that a plot of pressure versus time delay yields the ascending portion of the arterial waveform. These waveforms were compared with simultaneous invasive ascending aortic pressures in 57 adult patients (31 by fluid manometer [group A] and 26 by catheter-tipped micromanometer [group B]) during routine cardiac catheterization. Patient age ranged from 26 to 77 years. Eighty percent of group A patients and 40% of group B had coronary artery disease. Noninvasive systolic and diastolic pressures were very similar to invasive values in both groups (Pni = 0.98 x Pi, r = 0.99, p < 0.0001). Instantaneous pressure differences between waveforms were also similar in both groups, averaging between 4.5 and 5.5 mm Hg. Micromanometer and noninvasive pressure data were also obtained before and after intravenous nitroglycerin (n = 5) and isometric handgrip (n = 8) and demonstrated good agreement. A potential application of these pressures is for estimating maximal ventricular power to assess systolic function. This was tested using invasive pressure-volume data from four patients under a variety of conditions (exercise, pacing, etc.).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Arterial hemodynamics in human hypertension. Effects of angiotensin converting enzyme inhibition.

Previous studies have shown some distinct hemodynamic alterations in essential hypertension, including increased resistance, wave reflections, and pulse wave velocity and decreased systemic compliance. These abnormalities are completely normalized by nonspecific smooth muscle dilation with nitroprusside but not by combined alpha- and beta-adrenergic blockade. The renin-angiotensin system, acting possibly via both circulating and local tissue effects, is thought to play an important role in essential hypertension, so its role in the altered hemodynamics deserves careful investigation. A hypertensive patient group was compared with a normotensive group similar in age, body size, and proportion of men and women. During diagnostic cardiac catheterization, ascending aortic micromanometer pressures and electromagnetic flows were measured in the baseline state. Intravenous captopril of a sufficient dosage (11 mg) to normalize blood pressure then was given to the hypertensive patients while measurements were repeated. From the pressures and flows, aortic input impedance, wave reflection magnitude, and compliance were computed. In the hypertensive group, the important hemodynamic alterations consisted of increased peripheral resistance, first zero crossing of aortic impedance phase angle, and wave reflections and decreased systemic compliance. Captopril had a pronounced hemodynamic effect. It normalized blood pressure, resistance, and impedance phase angle zero crossing. Compliance, although increased substantially by captopril, was still slightly lower than normotensive levels. The magnitude of wave reflections, although substantially lowered by angiotensin converting enzyme inhibition, was still persistently greater than normal. The present results, together with those previously reported, demonstrate that a complex interplay of factors underlies the increased smooth muscle tone in essential hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Comparison of direct-current and radiofrequency ablation of free wall accessory atrioventricular pathways in the Wolff-Parkinson-White syndrome.

To evaluate and compare the safety and efficacy of catheter-mediated direct-current (DC) or radiofrequency (RF) ablation in patients with free wall accessory atrioventricular pathways, 95 patients with free wall accessory atrioventricular pathway-mediated tachyarrhythmias underwent catheter ablation. Immediately after ablation, 27 of 30 accessory pathways (90%) were ablated successfully with DC, but 2 of the 27 had early return of conduction and received a second ablation session; 3 of 8 (38%) and 57 of 62 (92%) accessory pathways were ablated successfully with RF through a small-tip (2 mm) and a large-tip (4 mm) electrode catheter, respectively. Complications in DC ablation included transient hypotension (2 patients) and pulmonary air-trapping (2 patients) and in RF ablation, cardiac tamponade (1 patient) and suspicious aortic dissection (1 patient); myocardial injury and proarrhythmic effects were more severe in DC ablation. Procedure and radiation exposure time were significantly longer in RF ablation (DC, 3.6 +/- 0.2 hours, 34 +/- 4 minutes; RF 4.2 +/- 0.5 hours, 50 +/- 10 minutes). This study confirms that RF ablation is associated with little morbidity and few complications, and RF ablation with a large-tip electrode catheter is an effective and relatively safe nonsurgical method for treatment of free wall accessory atrioventricular pathway-mediated tachyarrhythmias.

Adult↗
PubMed1992

Reversibility of left ventricular dysfunction after successful catheter ablation of supraventricular reentrant tachycardia.

Fourteen patients (mean age, 48 +/- 19 years) with left ventricular dysfunction in the absence of underlying organic heart disease underwent catheter ablation (nine with direct-current energy and five with radiofrequency energy) to treat drug-refractory, symptomatic supraventricular reentrant tachycardia (mean duration of tachycardia, 22 +/- 17 years). Clinical tachycardias were accessory pathway-mediated tachyarrhythmia (12 patients) and atrioventricular nodal reentrant tachycardia (two patients). Changes of ventricular function after successful ablation, as assessed by radionuclide ventriculography and echocardiography, showed a decrease in left ventricular end-systolic dimension (39 +/- 6 mm to 34 +/- 6 mm; 32 +/- 6 mm; p < 0.05) and in left ventricular end-diastolic dimension (55 +/- 5 mm to 52 +/- 3 mm; 51 +/- 3 mm; p < 0.05) in the early (2 to 3 months) and late (6 to 8 months) follow-up periods, increase of nuclear ejection fraction (38% +/- 8% to 46% +/- 7%; p < 0.05) and fractional shortening (28% +/- 7% to 36% +/- 8%; p < 0.05) in the late follow-up period. Increase of fractional shortening was mainly due to decrease in the end-systolic dimension. These findings suggest that prolonged attacks of uncontrolled supraventricular tachycardia may result in left ventricular dysfunction, which is reversible after successful catheter ablation of the arrhythmias.

Adult↗
PubMed1992

Catheter ablation of accessory atrioventricular pathways in 114 symptomatic patients with Wolff-Parkinson-White syndrome--a comparative study of direct-current and radiofrequency ablation.

To evaluate and compare the safety and efficacy of catheter-mediated direct-current and radiofrequency ablation in patients with Wolff-Parkinson-White syndrome, 114 patients with accessory pathway-mediated tachyarrhythmias underwent catheter ablation. Electrophysiologic parameters were similar in patients undergoing direct-current (group 1, 52 patients with 53 accessory pathways) and radiofrequency (group 2, 62 patients with 75 accessory pathways) ablation. Immediately after ablation, 50 of 53 accessory pathways (94%) were ablated successfully with direct current, but 2 of the 50 accessory pathways had early return of conduction and required a second ablation; 72 of 75 accessory pathways (96%) were ablated successfully with radiofrequency current. In the three accessory pathways in which radiofrequency ablation was unsuccessful, a later direct-current ablation was successful. During follow-up (group 1, 14 to 27 months; group 2, 8 to 13 months), none of the patients with successful ablation had a recurrence of tachycardia. Complications in direct-current ablation included transient hypotension (two patients), accidental atrioventricular block (one patient), and pulmonary air trapping (two patients); complications in radiofrequency ablation included cardiac tamponade (one patient) and suspicious aortic dissection (one patient). Myocardial injury and proarrhythmic effects were more severe in direct-current ablation. The length of the procedure and the radiation exposure time were significantly shorter in direct-current (3.5 +/- 0.2 hours, 30 +/- 4 minutes) than in radiofrequency (4.1 +/- 0.4 hours, 46 +/- 9 minutes) ablation. Findings in this study confirm the impression that radiofrequency ablation is associated with fewer complications than direct-current ablation and radiofrequency ablation with a large-tipped electrode catheter is an effective and relatively safe nonsurgical method for treatment of Wolff-Parkinson-White syndrome.

Atrial Fibrillation↗
PubMed1992

Reappraisal of electrical cure of atrioventricular nodal reentrant tachycardia--lessons from a modified catheter ablation technique.

A modified catheter ablation technique was studied prospectively in 29 patients with atrioventricular (AV) nodal reentrant tachycardia. A His bundle electrode catheter was used for mapping and ablation. Cathodic electroshocks (100-250 J) were delivered from the distal two electrodes (connected in common) of the His bundle catheter to the site selected for ablation. The optimal ablation site recorded the earliest retrograde atrial depolarization, simultaneous or earlier than the QRS complex, with absence of a His bundle deflection during AV nodal reentrant tachycardia. One additional electrical shock was delivered if complete abolition of retrograde VA conduction persisted for more than 30 min and AV nodal reentrant tachycardia was not inducible during isoproterenol and/or atropine administration. With a cumulative energy of 323 +/- 27 J and a mean of 2.3 +/- 0.5 shocks interruption or impairment of retrograde nodal conduction was achieved. Antegrade conduction, although modified, was preserved in 27 patients, with persistence of complete AV block in 2 patients. Two of the 27 patients still need antiarrhythmic agents to control tachycardia, the other 25 patients were free of tachycardia within a mean follow-up period of 13 +/- 2 months (range 7 to 20 months). Twenty-three patients received late follow-up electrophysiological studies (3-6 months after the ablation procedures), and the AV nodal function curves were classified into 4 types. The majority of the patients (15/23) had loss of retrograde conduction. Among the 8 patients with prolongation of retrograde conduction, 4 patients still had antegrade dual AV nodal property but all without inducible tachycardia. In conclusion, preferential interruption or impairment of retrograde conduction was the major, but not the sole, mechanism of electrical cure of AV nodal reentrant tachycardia.

Adult↗
PubMed1992

Radiofrequency catheter ablation for treatment of Wolff-Parkinson-White syndrome--short- and long-term follow-up.

One hundred and twenty-five patients with accessory pathways mediated tachyarrhythmias underwent radiofrequency ablation. Right-sided accessory pathways were ablated from the atrial aspect of the tricuspid anulus (all from the femoral vein approach) and the left-sided accessory pathways were ablated from the atrial or ventricular aspect of the mitral anulus. Immediately after the procedures, 3 of 8 accessory pathways (38%) and 131 of 137 accessory pathways (95%) were ablated successfully with radiofrequency through a small-tip (2 mm) and a large-tip (4 mm) electrode catheter, respectively. Seven of the 11 accessory pathways that failed radiofrequency ablation had a later successful direct current ablation. During follow-up (3 to 22 months), serial electrophysiological study showed that 11 of the 114 patients (10%) with successful ablation had return of accessory pathway conduction (2 had recurrence of tachycardia, 2%). Complications included accidental AV block (1 patient), cardiac tamponade (1 patient) and possible aortic dissection (1 patient). Transient proarrhythmic effects (more atrial and ventricular premature beats) were seen during the first week and sustained ventricular tachyarrhythmias were not inducible. In a successful session, procedure and radiation exposure times (including the time for diagnostic procedures) were 3.8 +/- 0.2 h and 45 +/- 4 min, respectively. This study confirms that radiofrequency ablation with a large-tip electrode catheter is an effective and relatively safe nonsurgical method for treatment of Wolff-Parkinson-White syndrome, with a low complication and recurrence rate.

Adult↗
PubMed1992

Catheter ablation of free wall accessory atrioventricular pathways in 89 patients with Wolff-Parkinson-White syndrome--comparison of direct current and radiofrequency ablation.

To evaluate and compare the safety and efficacy of catheter-mediated direct current (DC) or radiofrequency (RF) ablation in patients with free wall accessory atrioventricular pathways, 89 patients with free wall accessory atrioventricular pathway (AP)-mediated tachyarrhythmias underwent catheter ablation. Electrophysiological parameters were similar in the patients with DC (group I, 29 patients with 30 APs) or RF (group II, 60 patients with 64 APs) ablation. Immediately after ablation, it was seen that 27 of 30 APs (90%) had been ablated successfully with DC, but two of the 27 APs had early return of conduction and received a second ablation session; three of eight APs (38%) and 53 of 56 APs (95%) were ablated successfully with RF through a small-tip (2 mm) and a large-tip (4 mm) electrode catheter, respectively. Seven of the eight APs who had a failed RF ablation later had a successful DC ablation. During the follow-up (group I, 14 to 27; group II, 8 to 14 months), all successfully ablated patients had no recurrence of tachycardia. Complications in DC ablation included transient hypotension (two patients), and pulmonary air-trapping (two patients); in RF ablation the complications included cardiac tamponade (1 patient) and suspicious aortic dissection (1 patient); myocardial injury (reflected by peak CK-MB, 34 +/- 5 vs 15 +/- 4 IU.l-1) and pro-arrhythmic effects (new atrial and ventricular arrhythmias) were more severe in those who had DC ablation. Procedure and radiation exposure time were significantly longer in RF ablation (DC, 3.6 +/- 0.2 h, 34 +/- 4 min; RF 4.0 +/- 0.4 h, 46 +/- 10 min). This study confirms that RF ablation with a large-tip electrode catheter is an effective and relatively safe non-surgical method for treatment of free wall accessory atrioventricular pathway-mediated tachyarrhythmias.

Adult↗
PubMed1992

Reduced left ventricular compliance in human mitral stenosis. Role of reversible internal constraint.

BACKGROUND: The mechanisms of depressed left ventricular (LV) pump performance in human mitral stenosis (MS) remain poorly understood, because reduced filling alone affects many hemodynamic measurements. Therefore, pressure-volume relations were examined in nine subjects with MS and compared with eight age-matched normal controls. METHODS AND RESULTS: Data were obtained by conductance catheter/micromanometer technique with transient inferior vena cava occlusion used to alter load and generate pressure-volume relations. In a subset of patients (n = 5), data were obtained both acutely and at 3 months (n = 4) after balloon valvuloplasty. MS patients had reduced cardiac output (3.3 +/- 0.9 versus 5.6 +/- 1.7 l/min) and end-diastolic volume (68.0 +/- 6.9 versus 115 +/- 31 ml) versus controls (p less than 0.001), with a mean transvalvular gradient of 14 +/- 6 mm Hg and estimated valve area of 0.6 +/- 0.2 cm2. Systolic function as assessed by the end-systolic pressure-volume relation was virtually the same in MS and control subjects. In contrast, end-diastolic pressure-volume relations in MS were consistently shifted leftward and had an increased slope (lower compliance) at matched pressure ranges (6.5 +/- 3.0 versus 2.2 +/- 0.53 ml/mm Hg at a mean diastolic pressure of 8 mm Hg, p less than 0.001). This change was not a result of reduced LV filling or probably of increased right heart loading. Valvuloplasty acutely returned chamber compliance to near normal, a change that was sustained at 3-month follow-up. Systolic function was little altered at this time. CONCLUSIONS: These data indicate an impairment of diastolic function in human MS that can be acutely reversed by balloon valvuloplasty. Lowered LV compliance probably results from a functional restriction caused by ventricular attachment to a thickened and immobile valve apparatus.

Cardiac Catheterization↗
PubMed1992

Effective arterial elastance as index of arterial vascular load in humans.

BACKGROUND: This study tested whether the simple ratio of ventricular end-systolic pressure to stroke volume, known as the effective arterial elastance (Ea), provides a valid measure of arterial load in humans with normal and aged hypertensive vasculatures. METHODS AND RESULTS: Ventricular pressure-volume and invasive aortic pressure and flow were simultaneously determined in 10 subjects (four young normotensive and six older hypertensive). Measurements were obtained at rest, during mechanically reduced preload, and after pharmacological interventions. Two measures of arterial load were compared: One was derived from aortic input impedance and arterial compliance data using an algebraic expression based on a three-element Windkessel model of the arterial system [Ea(Z)], and the other was more simply measured as the ratio of ventricular end-systolic pressure to stroke volume [Ea(PV)]. Although derived from completely different data sources and despite the simplifying assumptions of Ea(PV), both Ea(Z) and Ea(PV) were virtually identical over a broad range of altered conditions: Ea(PV) = 0.97.Ea(Z) + 0.17; n = 33, r2 = 0.98, SEE = 0.09, p less than 0.0001. Whereas Ea(PV) also correlated with mean arterial resistance, it exceeded resistance by as much as 25% in older hypertensive subjects (because of reduced compliance and wave reflections), which better indexed the arterial load effects on the ventricle. Simple methods to estimate Ea (PV) from routine arterial pressures were tested and validated. CONCLUSIONS: Ea(PV) provides a convenient, useful method to assess arterial load and its impact on the human ventricle. These results highlight effects of increased pulsatile load caused by aging or hypertension on the pressure-volume loop and indicate that this load and its effects on cardiac performance are often underestimated by mean arterial resistance but are better accounted for by Ea.

Adult↗