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PubMedDate not supplied

The Maze procedure for the treatment of atrial fibrillation: a minimally invasive approach.

OBJECTIVES: The standard Maze procedure has proven to be extremely effective in curing atrial fibrillation in thousands of patients worldwide. Until now it has required a median sternotomy and cardiopulmonary bypass. In order to simplify the standard approach, a minimally invasive technique was developed. We have recently applied this minimally invasive Maze procedure in 72 patients. METHODS: The technique is dependent on the use of cryosurgery and the total number of atriotomies has been decreased from twelve to four. In addition to performing the Maze procedure, 32% of patients have had concomitant surgery via the minimally invasive approach including mitral valve repair/replacement and tricuspid valve repair. RESULTS: Perioperative morbidity is improved following the minimally invasive approach in comparison to the standard approach with the incidence of temporary perioperative arrhythmias being decreased by 50%. The long-term recurrence of atrial fibrillation is 2.4% following the minimally invasive Maze procedure and 2.2% following the standard Maze procedure. The incidence of pacemaker requirements following the standard Maze procedure is 20% but only 6% following the minimally invasive Maze procedure. Both right atrial and left atrial transport function have been documented in 100% of patients following the minimally invasive Maze procedure. CONCLUSIONS: We believe that the minimally invasive Maze procedure is a substantial improvement over the standard approach in terms of patient morbidity while preserving the effectiveness of the Maze procedure in curing atrial fibrillation.

Adult↗
PubMed1987

Noninvasive assessment by Doppler and M-mode echocardiography of hemodynamic responses to temporary pacing and to ventriculoatrial conduction.

A new, dual-chamber temporary pacing lead was introduced via the subclavian vein in 20 patients who needed a temporary pacemaker. Stroke volume (SV) was measured continuously by combining M-mode and noninvasive Doppler echocardiography during spontaneous rhythm (SR), AV sequential pacing at a positive AV interval (DP), ventricular pacing (VP) and AV sequential pacing at a negative AV interval (VA pacing). The valvular functions were determined by Doppler echocardiography. Left ventricular dimensions and function, and left atrial size were measured by M-mode echocardiography. In the nine patients with no valvular heart disease and with no ventriculoatrial (VA) conduction (group I) the CO increased 83 +/- 11% during DP and 42 +/- 9% during VP as compared to during SR when the heart rate (HR) was increased from 34 +/- 3 to 72 +/- 1 beats/min. The CO was 29 +/- 3% higher during DP than that during VP. In the seven patients with valvular heart disease and with no VA conduction (group II), the increment in CO compared to that during SR was 53 +/- 12% during DP and 31 +/- 11% during VP; the CO was 17 +/- 4% higher during DP than that during VP. In the four patients with spontaneous VA conduction (group III), the CO during DP was 35 +/- 10% greater than that during VP, which did not result in an increase in the CO compared to that during SR in spite of an increase in HR from 52 +/- 8 to 74 +/- 2 beats/min. The study demonstrated that DP is the preferred temporary pacing mode and also that VA conduction during VP resulted in a mean decrease of 20% in CO compared to that during VP without VA conduction. The hemodynamic benefit from DP compared to SR seems to decrease when the left ventricular end-diastolic dimension increases. Furthermore, patients with large left ventricular end-systolic dimensions seem to have a lower increase in stroke index during DP as compared to that during VP than patients with smaller end-systolic dimensions.

Aged↗
PubMed1997

AAIR versus DDDR pacing in patients with impaired sinus node chronotropy: an echocardiographic and cardiopulmonary study.

The aim of this study was to compare AAIR and DDDR pacing at rest and during exercise. We studied 15 patients (10 men, age 65 +/- 6 years) who had been paced for at least 3 months with activity sensor rate modulated dual chamber pacemakers. All had sick sinus syndrome (SSS) with impaired sinus node chronotropy. The patients underwent a resting echocardiographic evaluation of systolic and diastolic LV function at 60 beats/min during AAIR and DDDR pacing with an AV delay, which ensured complete ventricular activation capture. Cardiac output (CO) was also measured during pacing at 100 beats/min in both pacing modes. Subsequently, the oxygen consumption (VO2AT) and VO2AT pulse at the anaerobic threshold were measured during exercise in AAIR mode and in DDDR mode with an AV delay of 120 ms. The indices of diastolic function showed no significant differences between the two pacing modes, except for patients with a stimulus-R interval > 220 ms, for whom the time velocity integral of LV filling and LV inflow time were significantly lower under AAI than under DDD pacing. At 60 beats/min, CO was higher under AAI than under DDD mode only when the stimulus-R interval was below 220 ms. For stimulus-R intervals longer than 220 ms, and also during pacing at 100 beats/min, the CO was higher in DDD mode. The stimulus-R interval decreased in all patients during exercise. The time to anaerobic threshold, VO2AT, and VO2AT pulse showed no significant differences between the two pacing modes. Our results indicate that, at rest, although AAIR pacing does not improve diastolic function in patients with SSS, it maintains a higher CO than does DDDR pacing in cases where the stimulus-R interval is not excessively prolonged. On exertion, the two pacing modes appear to be equally effective, at least in cases where the stimulus-R interval decreases in AAIR mode.

Aged↗
PubMed1999

Atrial ejection force in patients with atrial fibrillation: comparison between DC shock and pharmacological cardioversion.

It is well known that the restoration of sinus rhythm is not always associated with the return of effective atrial contraction. Atrial ejection force (AEF) is a noninvasive Doppler derived parameter that measures the strength of the atrial contraction. The aim of the present study was to use pulsed-Doppler echocardiography to determine if different modalities of cardioversion influence the delay in the return of effective atrial contraction after cardioversion. DC shock and pharmacological therapy were compared. Sixty-eight patients were randomly cardioverted, either using DC shock or i.v. procainamide. The patients who were restored to a sinus rhythm had a complete Doppler echocardiographic examination within 1 hour after the restoration, after 24 hours, after 1 month, and after 3 months. AEF was measured and compared in the two groups of patients and within the same group. AEF was greater immediately and at 24 hours after cardioversion in patients who underwent pharmacological therapy compared to patients treated with DC shock (peak A wave, 60 +/- 9 vs 31 +/- 8 msec, P < 0.001; AEF 11.3 +/- 3 vs 5 +/- 2.9 dynes, P < 0.001). In both groups, AEF increases over time. In conclusion, AEF is a noninvasive parameter that can be easily measured after cardioversion and can give accurate information about the recovery of left atrial mechanical function. This finding may have important implications for guiding the anticoagulant therapy after cardioversion.

Anti-Arrhythmia Agents↗
PubMed1999

Evaluation of the Left Atrial Performance Using Acoustic Quantification.

In most clinical studies, evaluation of left atrial (LA) function evolved from estimation of LA size on chest radiograph, electrocardiographic P wave abnormalities, LA diameter determined at fluoroscopy or by echocardiography, LA pressure recordings, blood flow velocity with Doppler echocardiography, and measurements of LA volume based on echocardiographic, cineangiographic, radionuclide, and magnetic resonance imaging techniques. The recent development of real-time two-dimensional echocardiographic acoustic quantification (AQ) suggests that LA dimensions can be measured instantaneously to provide online assessment of its systolic and diastolic functions. By means of AQ echocardiography and simultaneous recordings of LA pressure, the LA pressure-area relation can be obtained. LA pressure-area relation consisted of two loops: the A loop, representing the LA pump function, and the V loop, representing LA reservoir and passive emptying functions. The importance of LA function has been demonstrated in congestive heart failure, atrial fibrillation, hypertension, and ischemic heart disease and during pacing or dobutamine infusion.

Journal Article↗
PubMed1999

Relationship Between Echocardiographic Determinants of Left Atrial Spontaneous Echo Contrast and Thrombus Formation in Patients with Rheumatic Mitral Valve Disease.

Spontaneous echo contrast (SEC) may be detected by ultrasonography in environments favoring blood stasis. It is most commonly seen through the use of transesophageal echocardiography in the left atrium of patients with rheumatic mitral valve disease especially in the presence of atrial fibrillation. We studied the predictors of SEC, such as cardiac rhythm, left atrium and left atrial appendage functions, and mitral and pulmonary vein flow parameters, in patients with rheumatic mitral valve disease. The relationship between these parameters and the severity of SEC and appearance of thrombus was evaluated.

Journal Article↗
PubMed2001

The normal sequence of right and left atrial contraction.

OBJECTIVE: To study the sequence of atrial activation and the interatrial electromechanical delay (IEmD) noninvasively in healthy subjects during sinus rhythm (SR). METHODS AND RESULTS: In 66 SR healthy subjects P-wave activation was analyzed by means of vectorcardiography. The timing of atrial contractions was measured as the intervals between the P-wave and the A-wave of the Doppler right and left ventricular inflows (P-A(t) and P-A(m)), and IEmD was calculated as the algebraic difference P-A(m)- P-A(t). In the horizontal plane the vectorcardiographic P-loop was anteroposterior ("typical", 41 subjects), anterior (18), or posterior (7). IEmD (mean +/- SE 17 +/- 8 ms) was directly related to R-R and P-R intervals. IEmD was significantly shorter in anterior and posterior P loops than in the typical (6.5 +/- 5.3 and 8.1 +/- 10.1, respectively, vs 24.2 +/- 3.1 ms). In the posterior P-loop group, who exhibited longer P-A(t), mitral E-wave velocity and E/A ratio were reduced, and left atrial booster function was increased. CONCLUSION: IEmD was widely variable in SR, reflecting the origin site of sinus impulse, which independently influenced ventricular filling dynamics.

Adolescent↗
PubMed1991

Local blood flow and glucose uptake within resting and exercising rabbit skeletal muscle.

A marked regional heterogeneity in blood flow at the level of large arterioles or small arteries is present within single skeletal muscles both in the dog and in the rabbit. A corresponding regional heterogeneity in metabolic activity could explain this phenomenon. We studied the correlation between regional blood flow and regional uptake of glucose within single muscles. Blood flow and glucose uptake were measured using the microsphere technique and the deoxyglucose method, respectively. Blood flow and glucose uptake were determined in 0.25-g regions from resting and stimulated muscles in anesthetized rabbits. Under resting conditions, no correlation between regional blood flow and regional glucose uptake (P greater than 0.05, 12 muscles) was observed. During stimulation, regional blood flow was positively correlated (0.4 less than r less than 0.6, P less than 0.05, 12 muscles) with regional glucose uptake. The coefficients of variation for regional blood flow and regional glucose uptake averaged approximately 0.35 and 0.23, respectively, both at rest and during stimulation. Specific fiber type distributions could not explain either the regional heterogeneity in blood flow or in glucose uptake. We conclude that regional blood flow within single skeletal muscles is not strongly linked to regional uptake of glucose. Both variables show considerable heterogeneity.

Adenosine Triphosphate↗
PubMed1998

Sensitivity of canine intrinsic cardiac neurons to H2O2 and hydroxyl radical.

To determine whether intrinsic cardiac neurons are sensitive to oxygen-derived free radicals in situ, studies were performed in 44 open-chest anesthetized dogs. 1) When H2O2 (600 microM) was administered to right atrial neurons of 36 dogs via their local arterial blood supply, neuronal activity either increased (+92% in 16 dogs) or decreased (-61% in 20 dogs), depending on the population of neurons studied. H2O2 (600 microM) administered into the systemic circulation did not affect neuronal activity, measured cardiac indexes, or aortic pressure. 2) The iron-chelating agent deferoxamine (20 mg/kg iv), a chemical that prevents the formation of oxygen-derived free radicals, reduced the activity generated by neurons (-57%) in 8 of 10 dogs. 3) H2O2 did not affect neuronal activity when administered in the presence of deferoxamine in these 10 dogs. 4) When the ATP-sensitive potassium (KATP) channel opener cromakalim (20 microM) was administered to intrinsic cardiac neurons in another 21 animals via their regional arterial blood supply, ongoing neuronal activity in 15 of these dogs decreased by 54%. 5) Neuronal activity was not affected by H2O2 when administered in the presence of cromakalim in 16 dogs. These data indicate that 1) some intrinsic cardiac neurons are sensitive to exogenous H2O2, 2) such neurons are tonically influenced by locally produced oxygen-derived free radicals in situ, and 3) intrinsic cardiac neurons possess KATP channels that are functionally important during oxidative challenge.

Animals↗
PubMed2001

Different patterns of interatrial conduction in clockwise and counterclockwise atrial flutter.

BACKGROUND: The terms counterclockwise (CC) and clockwise (C) atrial flutter (Afl) are used to describe right atrial activation around the tricuspid valve in the left anterior oblique view. The manner in which the left atrium is activated, as reflected by coronary sinus (CS) recordings, has not been systematically evaluated. METHODS AND RESULTS: Nine patients with both CC and C Afl underwent electrophysiological study with CS recordings during both rhythms with the use of a decapolar catheter with the tip placed in the distal CS. Patterns of CS activation during each type of Afl as well as during during sinus rhythm were categorized into 1 of 3 patterns: sequential proximal-to-distal, sequential distal-to-proximal, and fused, indicating activation from different directions. In 7 of 9 patients, the pattern of CS activation in CC Afl and C Afl differed, with a proximal-to-distal pattern in CC Afl and a fused pattern in C Afl. In 2 patients, pacing the high right atrial septum near the presumed site of Bachmann's bundle in sinus rhythm showed a similar fused pattern of CS activation. CONCLUSIONS: These results demonstrate different patterns of CS activation in CC Afl and C Afl in the majority of patients and are consistent with a model in which the left atrium is activated predominantly over Bachmann's bundle during C Afl and over the CS os in CC Afl. These findings may have implications for maintenance of Afl, interpretation of flutter wave morphology on surface ECG, and left atrial mechanical function in Afl.

Aged↗
PubMed1994

Hyaluronan efflux from canine lung with increased hydrostatic pressure and saline loading.

Although lymphatic washout of hyaluronan during lung hydration has been postulated to deplete lung interstitial hyaluronan content and thereby contribute to the decreased interstitial exclusion of albumin observed under these conditions, this hypothesis has not been directly tested. In anesthetized, ventilated mongrel dogs, a prenodal lung lymphatic was cannulated for measurement of lymph flow and hyaluronan concentration. Following baseline measurements, Pla was increased in four steps of 5 cm H2O in Group 1 or set to one pressure ranging between 6 and 32 cm H2O in Group 2. In Group 3, saline (15% body weight) was infused over 30 min and then Pla increased as in Group 2. Invariably, as lymph flow increased in Groups 1 through 3, lymph hyaluronan concentration and hyaluronan flux increased significantly (p < 0.05). In a separate control group, there were no changes in lymph flow, hyaluronan concentration, or hyaluronan flux. In Group 3, lung hyaluronan content at 5 h (0.76 +/- 0.08 mg/g dry weight) was not significantly less than that during baseline (0.88 +/- 0.05 mg/g dry weight), although total uronic acid content actually increased by 38% over the same time course. In contrast, in the control group, both lung hyaluronan and uronic acid content remained stable over the experimental period. From these data, approximately 2 to 3% of lung hyaluronan is predicted to leave the interstitium via lymphatic flux per day under baseline conditions. The daily turnover of interstitial hyaluronan by this route increased to 15 to 18% of total content when Pla was elevated and to 54% following saline infusion. Thus, lung hyaluronan can be rapidly mobilized with increased lymph flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗