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PubMed2002

Analysis of left atrial volume change rate during left ventricular diastolic phase with M-mode echocardiography for differentiation between normal and pseudonormal mitral inflow.

Pseudonormalization of mitral inflow is a diagnostic problem in clinical practice. An excellent correlation exists between the change in the left atrial (LA) angiographic area and posterior aortic wall motion. Therefore, we sought to define the role of LA wall motion, indicating LA volume change rate, in patients with normal and pseudonormal mitral inflow. We performed echocardiography after cardiac catheterization in 62 patients with a velocity ratio of early-to-late mitral inflow (E/A ratio) >1. Study patients were classified into 2 groups according to the response of mitral inflow to phase II of the Valsalva maneuver: patients with E/A >1 after the Valsalva maneuver (n = 31, control group), and patients with <1 after the Valsalva maneuver (n = 31, pseudonormal group). The slopes (slope E and A) of early diastolic and late diastolic motion of the LA wall were derived from M-mode analysis together with the time constant of left ventricular (LV) isovolumic relaxation from cardiac catheterization. The values of slope E (41 plus minus 11 vs 61 plus minus 12 mm/s, p <0.001) and slope E/A (0.69 plus minus 0.13 vs 1.32 plus minus 0.35, p <0.001) were significantly lower in the pseudonormal group and were inversely correlated with the time constant of LV isovolumic relaxation (r = 0.64, p <0.001 and r = 0.73, p <0.001, respectively). Using slope E/A <1 as an indicator of relaxation abnormality, the sensitivity, specificity, positive predictive value, and negative predictive value for the detection of pseudonormalization were 94%, 100%, 100%, and 94%, respectively. The slope of LA wall motion, indicating LA volume change rate, during the LV diastolic phase is useful for evaluating pseudonormal LV diastolic dysfunction in the selected patient population.

Adult↗
PubMed2003

Rotors and spiral waves in atrial fibrillation.

Despite many years of research, the mechanisms of atrial fibrillation (AF) are still poorly understood, and we currently are unable to adequately treat most patients with AF. Recently, the demonstration in both human and animal studies that the pulmonary veins (PVs) and the posterior left atrial (LA) wall play a substantial role in triggering and in driving the fibrillatory activity has opened new avenues for research into the mechanisms of initiation and maintenance AF at many levels of integration. This article focuses on recent studies at the whole-heart level that support the hypothesis that maintenance of AF, whether paroxysmal or persistent, may depend on the periodic activity of a small number of rotors in the posterior LA wall-PV region. These rotors activate the atria at exceedingly high frequencies and result in fibrillatory conduction. Recent clinical studies involving either segmental PV isolation or circumferential PV ablation support this view. Such encouraging results suggest that collaboration between basic and clinical electrophysiologists will lead to a more precise understanding of the manner in which rotors stabilize in the PV-LA junction, which should open new doors for the development of innovative approaches for the prevention, diagnosis, and treatment of AF.

Animals↗
PubMed2004

Evaluation of atrial refractoriness immediately after percutaneous mitral balloon commissurotomy in patients with mitral stenosis and sinus rhythm.

BACKGROUND: Chronic atrial stretch and rheumatic inflammatory activity leads to atrial dilatation and conduction slowing, and this increases the susceptibility to atrial fibrillation (AF). The aim of this study was to examine the effects of changes in the chronic atrial stretch on atrial refractoriness in the early period after percutaneous mitral balloon commissurotomy (PMBC) in patients with mitral stenosis and sinus rhythm. METHODS: Twenty-five patients undergoing PMBC were enrolled in this study. We evaluated the changes in pulmonary arterial pressure (PAP), left atrial (LA) pressure, mean mitral diastolic gradient, and mitral valve area in addition to the changes in atrial effective refractory periods (AERPs), AERP dispersion, and intra-atrial and interatrial conduction times after PMBC. RESULTS: There were significant decreases in mean diastolic gradient, PAP, mean LA pressure, and LA size after PMBC. Accompanying these acute hemodynamic changes after PMBC, AERPs in high right atrium (HRA), distal coronary sinus (DCS), and right posterolateral (RPL) were found to be increased (P <.001), and AERP dispersion, PA(HIS) (an interval between P wave on the surface electrocardiogram and atrial electrogram at the His bundle site), and HRA-DCS intervals were significantly reduced after PMBC (P <.001). It was revealed with linear regression and correlation analysis that only the changes in AERP dispersion were correlated with changes in LA pressure. CONCLUSIONS: Relief of chronic atrial stretch results in an increase in AERPs and decrease in AERP dispersion, suggesting the potential reversibility of the electrophysiological features of chronic atrial dilatation. Our study emphasizes that an acute reduction of chronic atrial stretch in mitral stenosis resulted in favorable effects on atrial electrophysiological characteristics, and our results provide the first detailed insights into the electrophysiological changes after PMBC in patients with sinus rhythm.

Adult↗
PubMed1996

Atrial fibrillation with left atrial spontaneous contrast detected by transesophageal echocardiography is a potent risk factor for stroke.

Nonrheumatic atrial fibrillation (AF) frequently coexists with other risk factors for cerebral ischemia. This study was originally designed to determine which combinations of clinical and echocardiographic abnormalities were most closely associated with the risk of cerebral ischemic events. Patients with cerebral ischemic events (n = 214) and community-based control subjects (n = 201) underwent transesophageal echocardiography and carotid artery imaging. Adjusted odds ratios (ORs) were determined using multiple logistic regression analysis. Independent risk factors for cerebral ischemia included diabetes, carotid stenosis, aortic sclerosis, left ventricular dysfunction, left ventricular hypertrophy, left atrial (LA) spontaneous contrast, and proximal aortic atheroma. Nonrheumatic AF in combination with LA spontaneous contrast and LA enlargement showed a strong association with cerebral ischemic events (OR 33.7 [95% confidence interval 4.53 to 251]). In subjects with sinus rhythm or nonrheumatic AF, LA enlargement was not associated with an increased risk of cerebral ischemic events in the absence of LA spontaneous contrast. However, only 2 patients and 1 control subject had nonrheumatic AF without LA spontaneous contrast or LA enlargement. Therefore, study of a larger number of subjects is required to address the issue of whether nonrheumatic AF itself carries increased risk. The combination of nonrheumatic AF with LA spontaneous contrast is a potent risk factor for cerebral ischemia. Ascertaining the risk factor in nonrheumatic AF requires adequate examination for underlying cardiac, aortic, and carotid vascular disease. Transesophageal echocardiography may contribute to this assessment.

Aortic Diseases↗
PubMedDate not supplied

Preoperative predictors of survival in patients with Thoratec ventricular assist devices as a bridge to heart transplantation. Thoratec Ventricular Assist Device Principal Investigators.

Approximately two-thirds of patients implanted with ventricular assist devices recover sufficiently to requalify for heart transplantation, and the other one-third die of complications that are often secondary to delayed ventricular assist device implantation and subsequent end-organ failure. To determine whether any preoperative predictors of survival exist, univariate statistics and multivariate stepwise logistic regression analysis were performed on pre-ventricular assist device demographics, hemodynamics, and blood chemistry in 186 patients receiving Thoratec ventricular assist devices (Thoratec Laboratories Corp., Berkeley, Calif.) while awaiting transplantation. The duration of circulatory support averaged 19.6 days (maximum, 226 days). One hundred thirty-seven patients (74%) received biventricular support, 47 received isolated left ventricular assist devices, and two received right ventricular assist devices. The average blood flow was 5.0 +/- 0.9 L/min. One hundred eighteen patients (63%) ultimately received heart transplants, of whom 96 patients were discharged. Age, gender, weight, and diagnosis were not related to survival, nor were preoperative cardiac index, pulmonary capillary wedge pressure, intraaortic balloon pumps, or cardiac arrests. Pre-ventricular assist device creatinine levels (p = 0.24) and total bilirubin levels (p = 0.09) were not significant, but blood urea nitrogen level (p = 0.02) and previous operations (p = 0.05) were related to survival, using univariate techniques. Patients with cardiac operations more than 30 days previously had the lowest survival-to-transplantation (39%) compared with patients with no previous operations (67%) or operations within the previous 30 days (61%). Blood urea nitrogen level was the only parameter found to be significant (p = 0.016) in a multivariate model.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2004

Left atrial volume in the prediction of first ischemic stroke in an elderly cohort without atrial fibrillation.

OBJECTIVE: To determine the clinical importance of left atrial (LA) volume in the prediction of first ischemic stroke. PATIENTS AND METHODS: This retrospective cohort study included randomly selected residents of Olmsted County, Minnesota, aged 65 years or older, who had undergone transthoracic echocardiography at least once at the Mayo Clinic in Rochester, Minn, between January 1, 1990, and December 31, 1998, were in sinus rhythm, and had no history of stroke, transient ischemic attack, atrial fibrillation, or valvular heart disease. Patients were monitored through medical records for first ischemic stroke or death. RESULTS: Of 1554 residents (59% women) aged 75+/-7 years, 92 (6%) had experienced at least 1 ischemic stroke over 4.3+/-2.7 years (incident stroke rate, 1.4 per 100 person-years). Left atrial volume of 32 mL/m2 or greater (hazard ratio [HR], 1.63; confidence interval [CI], 1.08-2.46) was independent of age (HR, 1.04; CI, 1.02-1.07), diabetes (HR, 1.91; CI, 1.07-3.41), myocardial infarction (HR, 1.64; CI, 1.01-2.64), and hyperlipidemia (HR, 1.55; CI, 1.01-2.37) for the prediction of first ischemic stroke. When quartiles of LA dimension were plotted against quartiles of indexed LA volume, a stepwise increase in risk with each quartile increment was evident only for indexed LA volume. Also, an LA volume of 32 mL/m2 or greater was associated with an increased mortality risk (HR, 1.30; CI, 1.09-1.56), independent of age, sex, and stroke status. CONCLUSIONS: In our elderly cohort with no prior atrial fibrillation, LA volume was independently predictive of first ischemic stroke, incremental to age, diabetes, myocardial infarction, and hyperlipidemia. It was also an independent predictor of death.

Aged↗
PubMed1990

Differentiation of sinus rhythms from supraventricular tachydysrhythmias by activation sequence and timing.

Implantable device detection of tachydysrhythmias remains unreliable and inexact. False responses may occur because of misinterpretation of sinus tachycardia (ST) as a supraventricular tachydysrhythmia (SVTD). Timing of atrioventricular (AV) activation and ventricular dispersion identified and discriminated between ST and SVTDs in 11 dogs. Three bipolar epicardial electrodes recorded left atrial and left and right ventricular depolarizations simultaneously during normal sinus rhythm (NSR) (mean of 5 beats in 11/11 dogs), ST produced by phlebotomy (50 beats in 10 episodes in 6/11) or isoproterenol infusion (105 beats in 21 episodes in 10/11), sinus bradycardia (SB) produced by vagal stimulation (140 beats in 29 episodes in 10/11), and during atrial flutter (AFL) (15 beats in 3 episodes in 3/11) and atrial fibrillation (AF) (152 beats in 31 episodes in 9/11) induced by programmed electrical stimulation. During lidocaine infusion, NSR (55 beats in 11 episodes in 10/11 dogs), SB (84 beats in 17 episodes in 7/11), AFL (10 beats in 2 episodes in 1/11), and AF (103 beats in 21 episodes in 7/11) were recorded. During isoproterenol infusion, SB (45 beats in 9 episodes in 5/11), AFL (15 beats in 3 episodes in 2/11), and AF (64 beats in 13 episodes in 5/11) were recorded in addition to ST. The interval between the left atrial and left ventricular intrinsic deflections (A-V1) and between the left and right ventricular intrinsic deflections (V1-V2) of each beat was measured. The mean value (msec) of A-V1 and V1-V2 in each episode was compared to NSR in the same dogs. A difference of greater than or equal to 16 ms was used for differentiation. In all cases except SB with first-degree AV block, V1-V2 in each episode was insignificant (0-14 msec), categorizing the rhythms as supraventricular. During NSR, ST and SB without AV block, delta A-V1 was small (0-15 msec). In contrast delta A-V1 was greater than or equal to 16 ms in 6/8 episodes of AFL. The remaining two episodes could be differentiated by the greater number of atrial versus ventricular beats. AF could be detected by the variability of A-V1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1997

Decrease in forces responsible for diastolic suction during acute coronary occlusion.

BACKGROUND: The production of left ventricular (LV) restoring forces generated during contraction, which are responsible for diastolic suction, is dependent on end-systolic volume (ESV) and systolic transmural and 3D deformation. We tested the hypothesis that acute coronary occlusion would result in loss of forces that cause suction. METHODS AND RESULTS: Ten open-chest dogs were subjected to a 10-minute acute coronary occlusion (proximal left anterior descending coronary artery). A servomotor connected to the left atrium (LA) was used to rapidly clamp LA pressure during systole below the level of the succeeding LV diastolic pressure, resulting in nonfilling diastoles during which the LV fully relaxed at its ESV. LA clamps at multiple ESVs (conductance catheter) allowed delineation of positive and negative portions of the fully relaxed LV pressure-volume relation (FRPVR). A negative fully relaxed pressure (FRP) indicates the presence of restoring forces. After 10 minutes of acute coronary occlusion, there was an upward shift of the FRPVR. Thus, for example, at matched ESVs before and during coronary occlusion, FRP was -1.1+/-1.1 (+/-SD) mm Hg before versus 0.2+/-1.2 mm Hg after 10 minutes of coronary occlusion (P<.05). CONCLUSIONS: Acute coronary occlusion results in a rapid decrease in forces responsible for suction. This phenomenon is independent of the level of ESV and may contribute to ischemic diastolic dysfunction.

Animals↗
PubMedDate not supplied

[Percutaneous mitral commissurotomy in patients with mitral valve stenosis and thrombosis of the left atrium].

UNLABELLED: Mitral percutaneous valvotomy (MPV) is an effective therapeutic alternative in the treatment of patients with mitral stenosis (MS) and thrombus in the left atrium have been an absolute contraindication to this procedure. The aim of our study is to evaluate the safety of MPV in patients with MS and thrombus in the appendix of the left atrium (ALA). Between September 1996 and April 1997, we performed ten procedures of MPV with Inoue's technique in patients with MS and thrombus in ALA. Nine females and 1 male were included. Their were 41 +/- 7.6 years old. The Wilkins score in our patients were 8 +/- 1.2. All were treated with oral anticoagulants between three and twelve months but the thrombus did not resolved. With transesophagic echocardiogram and fluoroscopic control we avoided the contact between wires and Inoue's catheter with ALA. Results were positive. Mitral valve area increased from 0.8 +/- 0.2 cm2 to 1.95 +/- 0.3 cm2. There was no case of systemic embolism or others major complications during the MVP and during following one year. CONCLUSION: MPV is a safe and efficient therapeutic alternative in the treatment of selected patients with MS and thrombus in ALA.

Adult↗
PubMedDate not supplied

Prevalence of interatrial block in the Program of All-Inclusive Care for the Elderly (PACE).

Interatrial block (IAB) (P wave > or =110 milliseconds) is a potent correlate of atrial tachyarrhythmias, left atrial electromechanical dysfunction, and embolism. IAB has been demonstrated to be highly prevalent in the general hospital population, but no investigation has addressed this in the elderly community outside the hospital. We appraised the prevalence of IAB in a service of the Program of All-Inclusive Care for the Elderly (PACE), the Elder Service Plan (ESP). Of the 202 ESP members in Worcester, MA, 167 (ages 61-103 years; female 81.4%) who had current 12-lead electrocardiograms were evaluated for IAB, and an age-based comparison was made between those with and without IAB. Of those patients with current electrocardiograms, 148 (88.6%) showed sinus rhythm and 72 (48.6%) depicted IAB: 20% in patients aged 60-69 years, 39.5% aged 70-79 years, 56.8% aged 80-89 years, and 50% in those 90 years and older. Given its sequelae of anatomic and pathophysiologic consequences, prompt recognition of IAB in a high-risk group such as that in the PACE community (48.6% prevalence) is important, especially for anticipation of atrial fibrillation and possible embolism.

Age Factors↗
PubMed1995

Effect of blood pH on pulmonary artery pressure, left atrial pressure and fluid filtration rate in isolated rabbit lung.

To determine the effects of pH changes on Pulmonary Artery Pressure (PAP), 18 isolated rabbit lung preparations, perfused with autologous blood mixture and constant PaCO2 have been studied. Each preparation was studied under 3 conditions: Baseline: 30 minutes equilibration period. Acidosis: pH was decreased by 0.2 N HCl infusion, the ventilatory rate was changed and different CO2 mixtures were used to maintain the PCO2 within the initial parameters. Compensated Acidosis (CA): pH was returned to normal values by 0.7 N NaHCO3 infusion maintaining PCO2 in its initial values. The decrease in pH (acidosis) from 7.36 +/- 0.05 to 7.18 +/- 0.06 at constant PCO2, generated a significant increase in PAP (13.6 +/- 3.2 cm H2O to 18.8 +/- 5.2 cm H2O, p < 0.01). The pH increase (CA) from 7.18 +/- 0.06 to 7.40 +/- 0.09 caused the PAP to decrease (18.8 +/- 5.2 cm H2O to 15.9 +/- 4.2 cm H2O); the fluid filtration rate remained unchanged during the whole experiment. It is concluded that blood pH changes at constant PCO2 result in significant changes of PAP. Acidemia produces pulmonary vasoconstriction, which may be a contributing factor in the genesis of pulmonary hypertension in clinical conditions with increased hydrogen ion concentration [H+].

Acidosis↗
PubMed2006

Relation of left atrial volume to B-type natriuretic peptide levels in patients with stable chronic heart failure.

This study assessed the relation between B-type natriuretic peptide (BNP) and echocardiographic indexes of left ventricular (LV) filling pressure in 53 patients with stable heart failure and without significant valvular dysfunction. Left atrial volume indexed to body surface area (LAVi), an indicator of chronic LV filling pressure, was correlated with BNP (r = 0.692, p <0.001) and was the strongest independent predictor of elevated levels in this cohort. LAVi was also the best predictor of BNP >or=100 pg/ml, with an area under the receiver-operating characteristic curve of 0.85 (95% confidence interval 0.74 to 0.96, p <0.001). Using the optimal cutoff of >31 ml/m(2), LAVi had a sensitivity of 92% and a specificity of 65% for BNP >or=100 pg/ml. Patients with LAVi >31 ml/m(2) had a median BNP of 122 pg/ml, compared with 21 pg/ml in patients with LAVi <or=31 ml/m(2) (p <0.001). These findings suggest that in patients with stable heart failure, BNP levels are related to chronic LV filling pressures. This may help explain the relatively modest correlation between BNP and acute measures of LV filling and the heterogeneity in BNP levels in patients with stable heart failure.

Aged↗
PubMed2001

Pharmacological properties of excitation-contraction mechanisms in isolated mouse left atria.

Effects of 4-aminopyridine (4-AP), nicardipine and ryanodine on the action potential and contractile force were examined in isolated mouse left atria. The mouse left atria had an action potential with an extremely short duration and two phases of repolarization; action potential duration at 50% repolarization was 6.7 +/- 0.4 ms (n = 15). The action potential duration, as well as contractile force, was increased by 4-AP (at 100 micromol/l and 1 mmol/l). Nicardipine (3 micromol/l), which is known to greatly reduce the contractile force in atria of most other experimental animal species, had no significant effect on the action potential and decreased contractile force by only 40% in mouse atria. Ryanodine (10 nmol/l) decreased the contractile force by 90% of basal value. At 100 nmol/l, ryanodine slightly affected the action potential configuration, which could be explained by indirect effects through inhibition of Ca(2+) release from the sarcoplasmic reticulum. The extremely short action potential duration and the highly sarcoplasmic reticulum-dependent contraction of the mouse atria appear to underlie its unique response to agonists.

4-Aminopyridine↗
PubMed1992

Hemodynamic interactions when combining verapamil, acute changes in extracellular ionized calcium concentration and enflurane, halothane or isoflurane in chronically instrumented dogs.

To assess the hemodynamic interactions when combining verapamil, acute changes in extracellular ionized calcium concentration [Ca2+] and enflurane (2.5%), halothane (1.2%) or isoflurane (1.6%), seven dogs were chronically instrumented to measure heart rate (HR), aortic, left atrial and left ventricular (LV) pressures, and cardiac output (CO). [Ca2+] was lowered 0.35 mmol.l-1 by citrate infusion and then increased 0.35 mmol.l-1 above control level by CaCl2 infusions. Verapamil was infused at 3 micrograms.kg-1 x min-1 (loading dose 200 (awake), 150 (isoflurane) or 100 (enflurane and halothane) micrograms.kg-1), giving mean verapamil concentrations around 75 (range of means: 66-84 ng.ml-1). Verapamil produced mostly minor changes in the cardiovascular effects of changing [Ca2+] in both awake and anesthetized dogs, indicating mostly additive effects. Verapamil induced a decrease in HR at high [Ca2+] and abolished an increase in mean aortic pressure at both low and high [Ca2+] awake. Verapamil exaggerated the decrease in CO and stroke volume (SV) induced by low [Ca2+] during enflurane anesthesia and abolished the increase in CO induced by low [Ca2+] and exaggerated the increase in SV and LV dP/dtmax induced by high [Ca2+] during halothane anesthesia.

Anesthesia, Inhalation↗
PubMed2001

Arrhythmogenesis in isolated rat hearts with enhanced alpha-adrenoceptor-mediated responsiveness.

1. It has been postulated that stimulation of myocardial alpha-adrenoceptors is one of the primary mediators of the dysrhythmias which occur during periods of myocardial ischaemia and reperfusion. This study examines arrhythmogenesis during coronary artery occlusion and reperfusion in isolated perfused rat hearts from control animals and from rats with enhanced myocardial alpha-adrenoceptor responsiveness. 2. Rats were administered propylthiouracil (PTU) in their drinking water for 8 weeks. This treatment resulted in an enhanced responsiveness of isolated left atria to the alpha-adrenoceptor agonist phenylephrine compared with atria from control animals. 3. In Langendorff-perfused isolated hearts, the spontaneous rate of contraction was significantly lower in the PTU-pretreated group than in either age-matched or weight-matched controls. Occlusion of the left anterior descending artery (LAD) for 25 min resulted in ventricular tachycardia (VT) of similar incidence and duration in all groups and ventricular fibrillation (VF) in both control groups but not the PTU-pretreated group. 4. Following the 25-min ischaemic period the myocardium was reperfused for 10 min. The incidence and duration of VT and VF during this period was similar in all groups except that the duration of VF in the PTU-pretreated group was significantly lower than in controls. 5. In perfused hearts paced at 4 Hz, the incidence and duration of dysrhythmias during ischaemia and reperfusion was again similar in all groups, only the duration of VF being affected (reduced) by PTU-pretreatment. 6. In conclusion, this study does not lend support to the hypothesis that myocardial alpha-adrenoceptors have a primary role in arrhythmogenesis, but the data would support a role for these receptors in myocardial protection.

Adrenergic alpha-Agonists↗
PubMed1996

Left ventricular diastolic suction with zero left atrial pressure in open-chest dogs.

We investigated left ventricular (LV) diastolic volume changes (suction inflows) with left atrial pressure (LAP) clamped to ambient pressure in six open-chest, anesthetized dogs. The left atrium was cannulated and connected to a servo pump, and LAP was clamped to a set point near 0 mmHg for four beats by withdrawing blood. LAP averaged 5.88 +/- 1.44 mmHg before the clamp and fell to 0.74 +/- 0.61 mmHg (P < 0.0001) after the clamp. During the first clamped beat a transmitral pressure gradient of 1.0 +/- 0.6 mmHg was observed, resulting in LV filling of 2.6 +/- 1.8 ml. Subsequent beats developed suction-driven (mean negative LV pressure: -1.5 +/- 1.3 mmHg; P < 0.005 vs. zero) LV filling of 4.5 +/- 2.8 ml/beat with a peak transmitral pressure gradient of 1.7 +/- 0.6 mmHg. These data are consistent with the hypothesis that LV suction can be an important filling mechanism under condition in which LV end-systolic volume is reduced, e.g., reduced filling pressures, high heart rates, exercise, or increased inotropic drive.

Animals↗
PubMed2003

Factors determining left atrial kinetic energy in patients with chronic mitral valve disease.

BACKGROUND: Increased left atrial (LA) work is a major contributor to LA fatigue, LA failure and atrial fibrillation in patients with mitral stenosis (MS) and mitral valvular regurgitation (MVR). The present study was undertaken to define factors that determine LA work in patients with chronic mitral valve disease. PATIENTS AND METHODS: Peak left atrial kinetic energy (LAKE)was used as an index of LA work in 14 patients with MS, 14 with MVR, and 19 normal subjects matched for age and gender with MS and MVR patients. LA stroke volume and ejection fraction were measured from the biplane area-length method using echo techniques. Peak LAKE was obtained from the formula 1/2 mv2, where m = LA stroke volume x 1.06 (blood's specific gravity) and v = transmitral Doppler A-wave velocity. RESULTS: Stepwise regression analysis often clinical and echocardiographic parameters demonstrated that in MS, mitral valve area (r2 = 0.43) and LA maximal volume (r2 = 0.62), in MVR, only LA maximal volume (r2 = 0.42) contributed independently to LAKE. LAKE was greater in MS and MVR compared to control subjects while LA ejection fraction was similar in all groups. CONCLUSIONS: It is concluded that LA work is markedly increased in patients with chronic mitral valve disease. Increased LA work in chronic mitral valve disease may contribute to LA fatigue, LA failure, and atrial fibrillation.

Adult↗
PubMed1991

Electrophysiological effects of sodium channel blockers on guinea pig left atrium.

The electrophysiological effects of five sodium channel blockers (mexiletine, lidocaine, disopyramide, aprindine and flecainide) on the guinea pig left atrium were investigated by recording the action potential and its maximum rate of rise (Vmax). The onset and offset kinetics of use-dependent block of Vmax were analyzed. Lidocaine, aprindine and flecainide were classified clearly as fast, intermediate and slow, respectively. Mexiletine and disopyramide had two components in onset and offset of use-dependent block. Mexiletine showed fast and intermediate kinetics, whereas disopyramide showed intermediate and slow kinetics. Action potential duration at 90% repolarization (APD) was prolonged by disopyramide and mexiletine. The other drugs did not change the action potential duration. Effective refractory period was prolonged by all drugs with relative potency in the following order: disopyramide greater than mexiletine greater than lidocaine greater than aprindine = flecainide. In conclusion, the modes of actions of sodium channel blockers on the atrium were disclosed to be different from those on the ventricle. The pharmacological therapy for atrial arrhythmias should be based on the electrophysiological effects of the drugs on the atrium, not on the ventricle.

Action Potentials↗