Acute resumption of conduction in the cavotricuspid isthmus after catheter ablation in patients with common atrial flutter. Real-time evaluation and long-term follow-up.

AIMS: Cavotricuspid isthmus conduction (CIC) is closely associated with the maintenance and recurrence of common atrial flutter (AFL). This study systematically sought to assess the prevalence and characteristics of acute CIC recovery during AFL ablation and to define its predictors and its relationship with the results of long-term follow-up. METHODS AND RESULTS: A total of 124 consecutive patients (105 men, 19 women, mean age 58 +/- 11 years) who underwent successful AFL ablation were included. The procedure endpoint was defined as complete bi-directional CIC block. During an observation period of 30 min, the incidence of CIC restoration was 34.% in patients and 39.8% in applications. It increased with increasing block time and decreased over time during the observation period. Block time in successful burns followed by persistent block was shorter than in those followed by CIC resumption (12 +/- 6 vs 33 +/- 12 s, P<0.0001). A negative correlation between block time and resumption time was found (r = - 0.57, P<0.001). Patients with permanent pacemakers had a higher incidence of acute CIC resumption than those without pacemakers (5/7 vs 29/117, P = 0.007). The AFL recurrence rate was 4.8% during a mean follow-up period of 21 +/- 8 months. Our results suggest that acute CIC resumption may be a potential risk for clinical AFL recurrence during long-term follow-up. CONCLUSIONS: Acute CIC resumption in common AFL ablation varies in terms of incidence and time course. Block time has a predictive value for acute CIC recovery. Observation time can be shortened if block time is short. With longer block time, it is essential to observe for a longer period in order to minimize CIC resumption.

[Atrial flutter--diagnosis and therapeutic possibilities]. / Atrieflutter--diagnostikk og behandlingsmuligheter.

BACKGROUND: Atrial flutter and atrial fibrillation are among the most common heart rhythm disturbances in the population, with an assumed prevalence of 1-2%. About 40,000-60,000 Norwegians endure such rhythm disorders, with an increasing occurrence in the elderly population. MATERIAL AND METHODS: Surface ECG remains the corner-stone for the clinical diagnosis. We describe the various mechanisms, clinical presentation, and diagnosis based on modern invasive electrophysiological methods of atrial flutter. RESULTS: The available therapeutic modalities for conversion during episodes and prophylaxis with drugs, various pacing techniques, DC conversion and surgical therapy are discussed. INTERPRETATION: Radiofrequency catheter ablation is the only available method to cure the patient in a gentle manner.

[Radiofrequency catheter ablation of atrial flutter]. / Radiofrekvenskateterablasjon av atrieflutter.

BACKGROUND: The anatomical structure of atrial flutter is now well recognized, and treatment with radiofrequency catheter ablation (RFA) is established. Several recording and ablation techniques can be applied. MATERIAL AND METHODS: An increasing number of patients have been treated with RFA at the Arrhythmia Centre at Haukeland University Hospital over the last six years. During the two-year period 1999 and 2000, a total of 108 procedures were performed for atrial flutter in a total of 84 patients. A total of 543 RFA procedures for various forms of re-entry tachycardias were performed during the same period; hence, atrial flutter comprised about 20% of RFA procedures. Altogether 71 men and 14 women with a mean age of 57 +/- 12 years were treated. The mean history of atrial flutter had a duration of nine years, maximum 43 years with several hospital admissions, drug trials, overdrive pacing and DC conversion until they were ultimately cured with RFA. RESULTS: The success rate during first time treatment was 96.5%. No serious complications were observed. INTERPRETATION: RFA should be the treatment of first choice in patients with recurrent or incessant atrial flutter.

[Myocardial injury in acute stroke assessed by troponin I]. / Myokardskade ved akutte hjerneslag bedømt med troponin I.

BACKGROUND: Acute ischaemic or haemorrhagic cerebrovascular events may produce myocardial damage. Cardiac troponin I is an indicator of cardiac cell injury with very high sensitivity and specificity. MATERIAL AND METHODS: We measured troponin I in 149 acute stroke patients admitted to the stroke unit of Trondheim University Hospital, Norway, in January to June 1999. RESULTS: 40 patients (27%) had troponin I values at 0.4 microgram/l or higher, indicating myocardial injury. 10 patients (6.7%) had troponin I values above 2.0 micrograms/l. Similarly, the mean value of CK-MB vas higher in the patients with myocardial injury, and these patients had more often ECG findings suggesting myocardial ischaemia. Patients with myocardial injury had a higher rate of previous TIA and heart failure. ECG showed atrial fibrillation in 13 of 39 patients with myocardial damage. Patients with detectable levels of troponin I had more embolic brain infarctions than thrombotic brain infarctions. Patients with myocardial injury did more often have abnormal values of CRP. 9 of 10 patients with troponin I-values above 2.0 micrograms/l had abnormal CRP values. No differences in glycosylated haemoglobin, cholesterol, heart rate, blood pressure or body temperature were found. Patients with the highest troponin I values had lower systolic blood pressure, and a higher heart rate, but these differences were not statistically significant. Patients with troponin I values above 2.0 micrograms/l had lower functional and neurological scores at admittance. Patients with myocardial injury were more often discharged to nursing homes. INTERPRETATION: Many patients with an acute stroke have at the same time a myocardial injury, determined by elevated troponin I values.

A typical P-wave morphology in incessant atrial tachycardia originating from the right upper pulmonary vein.

Automatic atrial tachycardias often originate from the ostia of the pulmonary veins. P-wave morphology during tachycardia may indicate from which pulmonary vein the tachycardia originates. Two patients with pulmonary vein tachycardias demonstrating atypical P-wave morphology were investigated. One of the patients had a tachycardia with two different cycle lengths. P-wave morphology was evaluated in 12-lead ECGs from two patients with incessant atrial tachycardia, during tachycardia and sinus rhythm. Their tachycardias were successfully ablated at the mouth of the right upper pulmonary vein. Previous studies have demonstrated a positive or negative P-wave configuration in lead aVL originating from this area and a change from a biphasic P-wave in V1 during sinus rhythm to a positive P-wave configuration during tachycardia. Neither of our two patients had such a change in lead V1. One our patients had two tachycardias with different cycle lengths originating from the same area. It is concluded that if an atrial tachycardia with P-wave morphology resembling that of sinus rhythm cannot be located to the right atrium, its origin may be the right upper pulmonary vein.

Left ventricular systolic and diastolic function assessed with two-dimensional and doppler echocardiography in "white coat" hypertension.

OBJECTIVES: The aim of this study was to investigate left ventricular function in subjects with "white coat" hypertension, defined as office arterial diastolic pressure > or = 90 and ambulatory daytime pressures < 140/90 mm Hg. BACKGROUND: The white coat arterial pressure response may, by influencing left ventricular function, have a confounding effect in studies of heart disease. METHODS: Two-dimensional and Doppler echocardiography combined with the calibrated subclavian arterial pulse tracing, were used to assess variables of left ventricular function in 26 subjects with white coat hypertension (office arterial diastolic pressure > or = 90 and < 115 mm Hg and ambulatory daytime diastolic pressure > or = 90 mm Hg) and 32 normotensive subjects. RESULTS: In subjects with white coat hypertension, systolic arterial pressure during the echocardiographic examination was significantly higher than ambulatory daytime systolic pressure. This pressure response was positively related to the ratio of the systolic to diastolic pulmonary venous flow peak velocities and to the peak velocity of flow reversion during atrial systole; it was inversely related to the ratio of early to late mitral flow peak velocities. Left ventricular stroke volume, ejection fraction and velocity of circumferential fiber shortening did not differ in the study groups, but left ventricular external work and end-systolic wall stress were increased in the white coat group. CONCLUSIONS: The arterial pressure response in subjects with white coat hypertension is associated with increased left ventricular external work, increased end-systolic wall stress and alterations of left ventricular filling but normal ejection fraction and velocity of circumferential fiber shortening.

Metformin improves blood lipid pattern in nondiabetic patients with coronary heart disease.

OBJECTIVES: To study whether the addition of metformin further improves the blood lipid pattern in non-diabetic patients with coronary heart disease already treated with lovastatin, diet and lifestyle advice. DESIGN: An open, prospective, randomized study in a university hospital setting. SUBJECTS: Sixty non-diabetic male patients previously treated with coronary artery bypass surgery or angioplasty and with serum cholesterol > or = 6.0 mmol L-1 and/or HDL-cholesterol < or = 1.2 mmol L-1. INTERVENTIONS: After a 4-week run-in period with lovastatin (40 mg day-1), and diet and lifestyle advice, patients were randomized into two groups, both continuing the run in treatment. One group received metformin up to 2000 mg day-1; the control group got no additional treatment. MAIN OUTCOME MEASURES: Fasting serum lipids, glucose and weight were registered at entrance (= week-4), and at weeks 0, 4 and 12. Changes from week 0 to week 4 and from week 0 to week 12 were compared. Side-effects of the treatment were also registered. RESULTS: Metformin lowered the LDL/HDL-cholesterol ratio by 12 and 6% at weeks 4 and 12, respectively, and reduced body weight by 1.8 kg at week 12. There was also a transient lowering effect on LDL-cholesterol and apolipoprotein B. In the normal weight subgroup of patients (body mass index < 27 kg m-2), metformin induced a decrease in total cholesterol (-9%). LDL-cholesterol (-12%). LDL/HDL-cholesterol ratio (-10%) and apolipoprotein B (-7%), as compared to the control group. In this subgroup, body weight and fasting glucose were unaffected by metformin. Thus, the lipid lowering effect in normal weight patients was not secondary to changes in body weight or fasting glucose. In overweight patients (body mass index > 27 kg m-2), metformin had no significant effects on blood lipids, but induced a weight loss of -3.0 kg and a transient reduction of fasting glucose. No side-effects were registered apart from those expected from each individual drug. CONCLUSIONS: Metformin given for 12 weeks as a supplement to lovastatin, diet and lifestyle advice to non-diabetic male patients with coronary heart disease further improves the lipid pattern in normal weight patients, and reduces weight in the overweight patients. Because metformin is cheap and other lipid lowering drugs are expensive, the potential of metformin as a lipid lowering agent should be further investigated.

Pulmonary venous flow velocities recorded by transthoracic Doppler ultrasound: relation to left ventricular diastolic pressures.

OBJECTIVES: This study was conducted to investigate whether pulmonary venous flow variables measured by transthoracic Doppler ultrasound can help identify patients with elevated left ventricular end-diastolic or filling pressures, or both. BACKGROUND: A widened left atrial pressure A wave occurs when left ventricular end-diastolic pressure is increased. Increased duration of pulmonary venous flow reversal at atrial systole might therefore be a marker for elevated end-diastolic pressure. Decreased systolic pulmonary venous flow is shown to be related to increased left ventricular filling pressure in studies using transesophageal Doppler echocardiography. METHODS: Left ventricular pressures at late diastole were measured by fluid-filled catheters in 50 consecutive patients undergoing diagnostic cardiac catheterization. Pulmonary venous and mitral flow velocities were recorded by transthoracic pulsed Doppler ultrasound. RESULTS: Adequate recordings were obtained in 45 patients. Pulmonary venous flow reversal exceeding the duration of the mitral A wave predicted left ventricular end-diastolic pressure > 15 mm Hg with a sensitivity of 0.85 and a specificity of 0.79. This difference in flow duration correlated well with the increase in ventricular pressure (r = 0.70, p < 0.001) at atrial systole and the end-diastolic pressure (r = 0.68, p < 0.001). The systolic fraction of pulmonary venous flow was markedly decreased (< 0.4) in all patients with a pre-A pressure (left ventricular pressure before atrial systole) > 18 mm Hg. CONCLUSIONS: Pulmonary venous flow reversal exceeding the duration of the mitral A wave indicates an exaggerated increase in left ventricular late diastolic pressure. Pulmonary venous systolic fraction < 0.4 suggests markedly increased ventricular filling pressure.

Cross-sectional left ventricular outflow tract velocities before and after aortic valve replacement: a comparative study with two-dimensional Doppler ultrasound.

To assess whether aortic valve replacement (AVR) results in changes in the flow velocity distribution in the left ventricular outflow tract (LVOT), 10 patients undergoing AVR for aortic stenosis were studied. By extracting velocity information from color flow maps as digital data, instantaneous cross-sectional velocity profiles were constructed. Velocity profiles obtained 1 to 3 days before AVR were compared with recordings made 3 months later. The LVOT velocity profiles were variably skewed both before and after surgery, and no systematic or uniform changes could be detected after AVR. The highest velocities were most often localized in the region from the center of the outflow tract diameter toward the septum both before and after surgery. At the time of peak flow the ratio of the maximum to the cross-sectional mean velocity was 1.38 +/- 0.13 before and 1.39 +/- 0.08 after AVR (NS), and the ratio of the maximum to the mean velocity time integral was 1.47 +/- 0.10 before and 1.56 +/- 0.10 after (NS). We conclude that AVR in patients with aortic stenosis does not result in a change in LVOT velocity profiles that will influence stroke volume estimates with the Doppler technique.

Two-dimensional echocardiography for prediction of aortic valve prosthesis size. A comparative study of Medtronic-Hall and Carpentier-Edwards supra-annular valves.

To assess the value of two-dimensional echocardiography (2D ECHO) for predicting prosthetic aortic valve size, the diameter of the aortic annulus was measured before implantation of a Medtronic-Hall valve in 24 patients and a Carpentier-Edwards supra-annular valve in 34. In the Medtronic-Hall group, the average prosthesis size was similar to the average annulus diameter, i.e. 23.2 +/- 2.1 vs 23.0 +/- 3.4 mm (NS), 95% confidence interval for the difference -1.0-0.7 mm. In the Carpentier-Edwards group the corresponding figures were 23.5 +/- 2.1 and 22.0 +/- 2.3 mm (p < 0.001), with 95% confidence interval 0.9-2.0 mm. Correlation between annulus diameter indicated by preoperative 2D ECHO and prosthesis size was stronger in the Medtronic-Hall (r = 0.88, p < 0.001) than in the Carpentier-Edwards group (r = 0.73, p < 0.001). The authors conclude that prosthetic aortic valve size may be accurately predicted by 2D ECHO, with Medtronic-Hall valve size similar to, and Carpentier-Edwards prostheses on average 1-2 mm larger than the 2D ECHO-estimated annulus diameter.

Cross-sectional early mitral flow-velocity profiles from color Doppler in patients with mitral valve disease.

BACKGROUND: Cross-sectional flow-velocity profiles from early mitral flow in 20 patients (10 with mitral regurgitation and 10 with mitral stenosis) were constructed from the velocity data from each point in sequentially delayed two-dimensional digital Doppler ultrasound maps. METHODS AND RESULTS: The data suggested that the early mitral flow studied in an apical four-chamber view was variably skewed in both patient groups. The maximum flow velocity overestimated the cross-sectional mean velocity at the same time by a factor of 1.12-1.86. The maximum time-velocity integral was 1.13-1.77-fold greater than the cross-sectional mean time-velocity integral. In patients with mitral regurgitation, the cross-sectional flow-velocity profile appeared to be most skewed at the level of the mitral leaflet tips. The level of the mitral annulus appeared to give the most homogenous flow-velocity distribution in both patient groups. CONCLUSIONS: When calculations of volume flow are based on pulsed Doppler ultrasound recordings with a single sample volume, the possibility of a skewed flow-velocity profile must be taken into account.

Impact of changes in heart rate and stroke volume on the cross sectional flow velocity distribution of diastolic mitral blood flow. A study on 6 patients with pacemakers programmed at different heart rates.

The effect of changes in stroke volume on the cross sectional velocity distribution in the mitral orifice during passive mitral inflow was studied in six patients with total atrioventricular block, atrial fibrillation and VVI pacemakers during periods with different heart rates. The time velocity integrals recorded both in the left ventricular outflow tract and at the mitral orifice decreased significantly as the heart rate was increased from 60 to 80 and from 80 to 100 beats per minute. Instantaneous cross sectional flow velocity profiles were constructed by time interpolation of the velocity data from each point in sequentially delayed two dimensional digital ultrasound maps. Each patient had a characteristic cross sectional flow velocity profile in the mitral orifice recorded at the level of the leaflet tips in a four chamber view. The velocity profiles varied between the patients. With increase in heart rate only minimal changes in the flow profiles from individual patients were seen. The maximum velocity through the mitral orifice overestimated the cross sectional mean velocity at the same time by a factor of 1.4-1.9. The maximum time velocity integral overestimated the cross sectional mean by a factor of 1.4-1.8. The observed cross sectional skew varied between patients but did not change significantly with increasing heart rate and decrease in stroke volume.

The velocity distribution in the aortic anulus in normal subjects: a quantitative analysis of two-dimensional Doppler flow maps.

The velocity distribution in the aortic anulus is commonly assumed to be uniform. A skewed velocity profile may have consequences for the accuracy of volume flow estimates by the Doppler echocardiographic technique. To assess this issue, the velocity distribution in the aortic anulus in 12 normal subjects was studied by computer analysis of digital velocity data from two-dimensional Doppler ultrasound flow maps. The velocity profiles in the aortic anulus were found to be flat but slightly skewed, with the highest velocities toward the septum. There was little interindividual variation. Our findings imply that the centerline velocity is the best estimate for the spatial mean velocity at the aortic anulus in normal subjects. The importance of this finding in patients is unknown. In normal subjects, the results suggest that stroke volume might be overestimated by approximately 15% by Doppler echocardiography if the cross-sectional velocity profile is not accounted for.

Validity of an early postoperative baseline Doppler recording after aortic valve replacement.

In 131 patients undergoing aortic valve replacement (53 bioprostheses, 78 mechanical), the pressure decrease across the prosthesis was recorded with Doppler ultrasound at a baseline study early postoperatively (mean 11 +/- 5 days) and compared with a repeat measurement 3 to 5 months later. At baseline the hemodynamic state was markedly different, with increased heart rate (89 +/- 14 vs. 74 +/- 13 beats/min, p less than 0.001) and decreased left ventricular ejection time index (367 +/- 21 vs 390 +/- 22, p less than 0.001). A minor and clinically insignificant decrease in pressure decrease with time was found. The 95% confidence interval for the difference was 0.2 to 3.0 and 0.2 to 1.7 mm Hg for the peak and the mean pressure decrease, respectively. The change in pressure decrease was statistically significant for bioprostheses (mean 16 +/- 5 vs 14 +/- 4 mm Hg, p less than 0.01) and smaller (less than or equal to 23 mm) valves (mean 17 +/- 4 vs 15 +/- 4 mm Hg, p less than 0.01), whereas no significant changes were found for mechanical valves or valves of a larger size. The change in mean pressure decrease from baseline to the second examination was within +/- 5 mm Hg for 82% of patients. It is concluded that despite a different hemodynamic state in the early postoperative period, the pressure decrease across aortic valve prostheses obtained at this time can be used as a reference for later comparison.

Sensitivity and speed of colour Doppler flow mapping compared with continuous wave Doppler for the detection of ventricular septal defects.

Twenty nine patients (aged from three months to 37 years) with confirmed or suspected ventricular septal defects were studied separately by three examiners who used colour flow mapping and imaging, or continuous wave Doppler and imaging, or a combined reference examination. Colour flow mapping identified 19 of the 25 patients with a ventricular septal defect, continuous wave Doppler echocardiography identified 18, and the combined reference examination identified 24. Two of four patients without ventricular septal defect had a false positive result with colour flow mapping and none had a false positive result with continuous wave Doppler examination. During the reference examination continuous wave Doppler identified 24 patients with ventricular septal defects and colour flow mapping identified 23. In two patients a second ventricular septal defect was found by colour flow mapping, and confirmed by continuous wave Doppler. There was no significant difference in time to diagnosis between the two techniques. Colour flow mapping aids identification of multiple ventricular septal defects but is not faster and has lower specificity than continuous wave Doppler. A combination of the two techniques gave the highest sensitivity and specificity.

Instantaneous cross-sectional flow velocity profiles: a comparative study of two ultrasound Doppler methods applied to an in vitro pulsatile flow model.

Two methods based on different techniques for construction of cross-sectional flow velocity profiles from Doppler ultrasound signals were compared: an intraluminal method using pulsed-wave Doppler echocardiography and an extraluminal method using two-dimensional (color) Doppler ultrasound. The methods were applied to an in vitro pulsatile flow model. With the intraluminal method, pulsed Doppler recordings obtained throughout several flow pulses at different positions across a tube were digitized, and cross-sectional flow velocity profiles were obtained by matching the onset of flow velocity at the various positions. With the extraluminal method, cross-sectional flow velocity profiles were obtained by time interpolation between the digital flow velocity data obtained from several flow velocity maps. The first flow velocity map was recorded at onset of flow and the following maps were incrementally delayed with 20 msec from one flow pulse to the next. The time lag caused by the time needed to update each of the flow velocity maps was compensated for by time interpolation between the sequentially recorded flow velocity maps. The cross-sectional flow velocity profiles obtained with the two methods were compared at identical positions within the tube model at equal flow settings and throughout the pulsatile flow periods. At three different flow settings with peak flow velocity of 0.3, 0.5, and 0.7 m/sec, the difference (mean +/- SD) between the obtained velocities were 0.01 +/- 0.04, -0.01 +/- 0.05, and -0.03 +/- 0.07 m/sec, respectively. The findings suggest that cross-sectional flow velocity profiles from pulsatile flow velocity recordings can be obtained equally well with both methods.

Estimation of arterial compliance in aortic regurgitation: three methods evaluated in pigs.

Three methods for measuring arterial compliance when aortic regurgitation is present are examined. The first two methods are based on a Windkessel model composed of two elements, compliance C and resistance R. Arterial compliance was estimated from diastolic pressure waveforms and diastolic regurgitant flow for one method, and from systolic aortic pressure waveforms and systolic flow for the other method. The third method was based on a three-element Windkessel model, composed of characteristic resistance r, compliance C and resistance R. In this method arterial compliance was calculated by adjusting the model to the modulus and phase of the first harmonic term of the aortic input impedance. The three methods were compared and validated in six anaesthetised pigs over a broad range of aortic pressures. The three methods were found to give quantitatively similar estimates of arterial compliance at mean aortic pressures above 60 mm Hg. Below 60 mm Hg, estimates of arterial compliance varied widely, probably because of poor validity of the Windkessel models in the low pressure range.

Quantification of aortic regurgitation by Doppler echocardiography: a new method evaluated in pigs.

We have developed a method to quantify aortic regurgitant orifice and volume, based on measurements of the velocity of the regurgitant jet, aortic systolic flow, the systolic and diastolic arterial pressures, a Windkessel arterial model, and a parameter estimation technique. In six pigs we produced aortic regurgitant flows between 2.1 and 17.8 ml per beat, i.e. regurgitant fractions from 0.06 to 0.58. Pulmonary and aortic flows were measured with electromagnetic flow probes, aortic pressure was measured invasively, and the regurgitant jet velocity was obtained with continuous-wave Doppler. The parameter estimation procedure was based on the Kalman filter principle, resulting primarily in an estimate of the regurgitant orifice area. The area was multiplied by the velocity integral of the regurgitant jet to estimate regurgitant volume. A strong correlation was found between the regurgitant volumes obtained by parameter estimation and the electromagnetic flow measurement. These results from our study in pigs suggest that it may be possible to quantify regurgitant orifice and volume in patients completely noninvasively from Doppler and blood pressure measurements.

Cross sectional early mitral flow velocity profiles from colour Doppler.

Instantaneous cross sectional flow velocity profiles from early mitral flow in 10 healthy men were constructed by time interpolation of the velocity data from each point in sequentially delayed two dimensional digital Doppler ultrasound maps. This interpolation allows correction of the artificially produced skewness of velocities across the flow sector caused by the time taken to scan the flow sector for velocity recording of pulsatile blood flow. These results suggested that early mitral flow studied in an apical four chamber view is variably skewed both at the leaflet tips and at the annulus. The maximum flow velocity overestimated the cross sectional mean velocity at the same time by a factor of 1.2-2.2. Also the maximum time velocity integral overestimated the cross sectional mean time velocity integral to the same extent. This cross sectional skew must be taken into account when calculation of blood flow is based on recordings with pulsed wave Doppler ultrasound from a single sample volume.