Optimal electrogram voltage recording technique for detecting the acute ablative tissue injury in the human right atrium

Background: The optimal recording technique of the electrogram voltage for detecting abnormal atrial tissue remains unclear. The aim of this study was to compare the impact of various recording techniques on the electrogram voltage after the delivery of ablation therapy in the human right atrium (RA).
Material and Methods: Noncontact mapping was performed in 27 patients with typical atrial flutter (mean age = 63 ± 16, males = 20). Noncontact unipolar and bipolar electrograms were obtained before and after cavotricuspid isthmus (CTI) linear ablation. All unipolar electrograms were acquired with both wide-band filtering (0.5–300 Hz) and narrow-band filtering (32–300 Hz). The unipolar voltage measurements included both the peak-to-peak voltage and peak-negative voltage (PNV) for both filter settings.
Results: A comparison of the electrogram voltage along the ablation line before and after the ablation demonstrated a greater reduction in the unipolar PNV with wide-band filtering (70 ± 24%) than in any of the other recording modalities (P = 0.03). It was the most sensitive and specific recording technique to predict conduction block (cut-off Value 0.35 mV; sensitivity = 94.4% and specificity = 80%). A comparison of the electrogram voltage between the ablated atrial myocardium and nearby nonablated myocardium showed that the unipolar PNV with the wide-band filtering remained the most sensitive method to detect the acute ablative tissue injury, whereas the peak-to-peak bipolar voltage was the most specific method.
Conclusion: The noncontact unipolar electrogram using the PNV with wide-band filter settings (0.5–300 Hz) provided the most sensitive recording technique for detecting acute ablative tissue injury.     

Human ventricular refractoriness. Effects of cycle length, pacing site and atropine.

The effective refractory period of the right ventricle (ERP-V) was measured in 27 patients during atrial or ventricular pacing using the ventricular extra stimulus method. Pacing was conducted with impulses of 1.5-2 times diastolic threshold. The ERP-V was directly related to the basic cycle length (BCL) although the ERP-V was always greater for atrial pacing than for ventricular pacing at a given BCL. The ratio ERP-V/BCL was greater at shorter cycle lengths indicating that a larger fraction of the cycle was refractory at faster heart rates. The ratio ERP-V/QT interval did not change over a range of BCLs, but the ratio was larger for atrial pacing (.77 +/- .05 SD) than for ventricular pacing (.60 +/- .05). Atropine (1 mg i.v.) was given to six patients. The drug did not affect the ERP-V in six of eleven determinations, prolonged ERP-V twice and shortened it slightly three times. Measurements were reproducible over an hour but varied at a given BCL when measured on separate days. Asymptomatic repetitive beating occurred in seven of 27 patients when the premature stimulus was within 20 msec of the ERP-V. The effective refractory period of the right ventricle in man can be determined reproducibly and with safety. Changes induced by various perturbations parallel results from in vitro single cell and myocardial studies.     

The intracellular fate of Histoplasma capsulatum in human macrophages is unaffected by recombinant human interferon-gamma

Human alveolar, peritoneal, and cultured macrophages were exposed in vitro to human recombinant interferon-gamma (rHuIFN-gamma) and were tested for their ability to inhibit intracellular replication of yeast-phase Histoplasma capsulatum. Exposure at various concentrations, and for different time periods, failed to activate the macrophages to inhibit multiplication of intracellular yeast. Macrophages were, however, activated by rHuIFN-gamma as shown by their ability to inhibit intracellular replication of Trypanosoma cruzi and by their enhanced production of superoxide when stimulated by phorbol myristate acetate. These data indicate that rHuIFN-gamma by itself does not activate human macrophages to inhibit intracellular proliferation of yeast-phase H. capsulatum.     

Shock secondary to extrinsic compression of the right atrium by postoperative mediastinal hematoma. Pseudotumor echocardiography image in right atrium

We present the case of a 64 year-old patient in whom an aortic Saint Jude prosthesis, a Cosgrove's mitral annulus and triple coronary artery by-pass graft were implanted, and who presented with shock related to extrinsic compression of the right atrium by a mediastinal hematoma within the first postoperative month. Transthoracic echocardiogram showed a right atrial , hampering right atrium drainage. The extrapericardial location of the hematoma is of note and was diagnosed with the aid of thoracic computerized tomography. We present the case of a 64 year-old patient in whom an aortic Saint Jude prosthesis, a Cosgrove's mitral annulus and triple coronary artery by-pass graft were implanted, and who presented with shock related to extrinsic compression of the right atrium by a mediastinal hematoma within the first postoperative month. Transthoracic echocardiogram showed a right atrial , hampering right atrium drainage. The extrapericardial location of the hematoma is of note and was diagnosed with the aid of thoracic computerized tomography.     

Cold-induced arrhythmias in the isolated rabbit atrium studied by mapping

Arrhythmias developing in isolated rabbit atria following the cooling of the perfusion solution were studied by multielectrode mapping. In 10 out of the 12 initially invulnerable preparations, the cooling to 27 +/- +/- 0.7'C induced arrhythmias. The effect was reversible, disappearing with the temperature normalization. Mapping showed that in 60% of the cases the arrhythmias were caused by the emergence of the leading cycles (functionally determined re-entry). In 40% of the cases, the re-entry was not demonstrable by mapping. However, arrhythmias in these experiments developed at the same temperature and had the same period as the leading cycles. The appearance of arrhythmias was closely correlated with a decrease in the wave length which strongly suggests the re-entry mechanism of hypothermic arrhythmias.     

Atrial natriuretic polypeptide is removed by the lungs and released into the left atrium as well as the right atrium in humans

To examine the sites of release and removal of plasma atrial natriuretic polypeptide plasma levels in the femoral vein, right atrium, pulmonary artery, pulmonary capillary bed, left atrium and aortic root were measured in 11 control subjects and 22 patients with mitral stenosis. Mean plasma natriuretic polypeptide levels in the femoral vein, right atrium, pulmonary artery, pulmonary capillary bed, left atrium and aortic root were, respectively, 64 +/- 29, 124 +/- 72, 103 +/- 44, 83 +/- 30, 106 +/- 46 and 101 +/- 35 pg/ml in the control subjects and 321 +/- 170, 500 +/- 234, 458 +/- 266, 356 +/- 209, 434 +/- 222 and 432 +/- 217 pg/ml in the patients with mitral stenosis. In both the control subjects and the patients with mitral stenosis, there was a significant increase between the femoral vein and the right atrium and between the pulmonary capillary bed and the left atrium and a significant decrease between the pulmonary artery and the pulmonary capillary bed. Blood samples were also taken simultaneously from the pulmonary vein and the pulmonary capillary bed, as well as from the pulmonary artery and the left atrium, in 25 patients (11 control subjects, 5 patients with mitral stenosis and 9 patients with atrial septal defect). There was no difference in plasma atrial natriuretic polypeptide levels between the pulmonary capillary bed and the pulmonary vein in these 25 patients. It is concluded that atrial natriuretic polypeptide 1) is released into the left as well as the right atrium, and 2) is removed by the lungs.     

Synovial sarcoma in the right atrium and right ventricle

A metastatic synovial sarcoma in the right atrium and ventricle is described. A 36-year-old man was admitted to our hospital with generalized fatigue, dyspnoea, and precordial pain. Transthoracic echocardiography demonstrated a metastatic tumour in both the right atrium and right ventricle and revealed obstruction of the inflow tract of the right ventricle caused by a metastatic right atrial tumour. Thoracic computed tomography revealed a pleural-based paravertebral mass in the left intrathoracic cavity and multiple pulmonary nodules in both lungs. Cardiac surgery was performed for palliative treatment due to right cardiac failure and a risk of fatal embolization. The patient died 12 months after the cardiac surgery.     

The human atrial strength-interval relation. Influence of cycle length and procainamide

We defined the atrial strength-interval relation in 23 patients at cycle lengths of 600, 450, and 300 msec before and after procainamide. The atrial diastolic threshold was similar at cycle lengths of 600 and 450 msec, but the threshold at 300 msec was significantly higher than that determined at 600 and 450 msec both before and after procainamide. Procainamide significantly increased the diastolic threshold only at a cycle length of 300 msec. The strength-interval relation was nonlinear, showing progressively decreasing decrements in the measured refractory period as the stimulating current was increased. Progressive decreases in the drive cycle length from 600 to 450 to 300 msec caused similar decreases in refractory periods. The shape of the curves was similar at cycle lengths of 600 and 450 msex. However, at low current strengths, the slope of the curve determined at 300 msex was significantly more vertical than the slopes of the curves at the longer drive cycle lengths. Procainamide caused similar increases in apparent refractory periods at each paced cycle length. Procainamide did not alter the shape of the curves at any paced cycle length. These observations confirm the importance of stimulation frequency on atrial excitability. They suggest that the effects of procainamide on the effective refractory period of the atrium are not cycle length dependent, although the drug effects on threshold are dependent on the drive cycle length.     

The interrelation between the monophasic action potential duration, cycle length and ischaemia in the human left ventricle.

Steady state monophasic action potentials were recorded from a single site in the left ventricular endocardium during incremental atrial pacing to the point of angina in 25 patients. Ischaemic areas of the left ventricle were documented using a perfusion marker (99mTc-MIBI) simultaneously with the action potential recording procedure. Recordings were obtained from an ischaemic area in 13 patients and from a non-ischaemic area in 12. A linear correlation between action potential duration and cycle length changes was demonstrated for both ischaemic and non-ischaemic zone recordings between cycle length changes of 750 and 428 ms. Ischaemia induced a shortening of the action potential duration significantly greater than that produced by cycle length changes (P less than 0.0001). Mean action potential duration shortening corrected for 100 ms change in cycle length for ischaemic zone recordings was 31.4 +/- 4.2 (SD) compared to 23.3 +/- 3.1 ms for non-ischaemic zone recordings. A range of values of action potential duration shortening in unit time was analysed for sensitivity and specificity for the detection of ischaemia. A value of 26.5 ms per 100 ms change in cycle length provided the optimum compromise with 88% sensitivity and specificity. Our data provide a means of employing the monophasic action potential duration to quantify early localized ischaemia in the presence of an alteration in cycle length.     

Endocardial mapping of atrial fibrillation in the human right atrium using a non-contact catheter.

BACKGROUND: Endocardial mapping of atrial fibrillation in humans is limited by its low resolution and by complexities in the arrhythmia and atrial anatomy. METHODS AND RESULTS: A catheter mounted non-contact multielectrode was deployed in the right atrium of 11 patients with atrial fibrillation and used to reconstruct 3360 electrograms, superimposed onto a computer-simulated model of the endocardium, using inverse solution mathematics. This allows construction of isopotential maps of the right atrium. Patients had either sustained atrial fibrillation (n=3) for >6 months or developed atrial fibrillation during the study (n=8). Spontaneous initiation of atrial fibrillation was recorded in one patient and was demonstrated by the non-contact system to arise from two successive atrial ectopic beats from the site of a roving contact catheter. Reconstruction of electrograms recorded during atrial fibrillation was validated by comparison with contact electrograms with cross-correlation. During established atrial fibrillation, four patients predominantly had a single right atrial wave front, two had two wave fronts and five patients had three to five wave fronts for most of the time. Periods of electrical silence were seen in the right atrium in eight patients, after which, activity emerged from consistent septal sites alone, suggesting a left atrial origin. During intravenous administration of flecainide, atrial fibrillation in two patients terminated spontaneously or following pacing manoeuvres, while in the remaining patient sinus rhythm was restored via atrial tachycardia. CONCLUSION: Non-contact mapping of the right atrium has demonstrated modes of initiation and termination of atrial fibrillation, characterized different patterns of right atrial activation in atrial fibrillation and suggests that the left atrium may sustain atrial fibrillation in some patients. Simultaneous mapping of the right and left atrium is required to further elucidate the mechanisms of human atrial fibrillation.     

The importance of derived 12-lead electrocardiography in the interpretation of arrhythmias detected by Holter recording.

Holter monitoring has been used extensively for the detection, diagnosis, and evaluation of therapy for cardiac arrhythmias. The availability of three-channel monitors allows for the recording of vectorcardiographic leads X, Y, and Z. One method, which was recently described by Dower et al., (J Electrocardiol 1988;21:5182-7), uses modified vectorcardiographic leads and allows for the acquisition of a derived 12-lead ECG of selected rhythm strips during the recording. In the present study, we evaluated the usefulness of the derived 12-lead ECG in the detection of P-wave and ST-segment shifts, assessment of QRST changes, and distinction between ventricular ectopic and aberrant supraventricular complexes. Our preliminary findings indicate that careful analysis of the derived 12-lead ECG provides additional information for a more accurate diagnosis of arrhythmias that are detected by the Holter monitor. The clinical importance and cost-effectiveness of the derived 12-lead ECG needs further evaluation.     

Primary angiosarcoma of the right atrium detected by magnetic resonance imaging.

A 20-year-old woman with a primary angiosarcoma of the right atrium is reported. The patient had a cardiorespiratory arrest due to cardiac tamponade with bloody pericardial effusion. Magnetic resonance imaging (MRI) revealed a tumor, which was corroborated by selective coronary angiography. Open-heart surgery was performed. The tumor relapsed however, and she died four months after operation. The tumor was undetectable by echocardiography, but MRI demonstrated a heterogeneous mass with focal areas of high- and low-signal intensity in the right atrium, suggesting that MRI may allow characterization of cardiac tumors.     

Divided right atrium. Diagnosis by echocardiography, and considerations on the functional role of the Eustachian valve.

A child presented at birth with severe cyanosis. Echocardiography showed hypoplasia of the right heart with a right-to-left shunt at atrial level. A conservative approach was adopted initially, and the situation improved over a few months, with reversal of the atrial shunt. Surgery was successfully performed at 4 years of age after further echocardiography revealed a congenitally large Eustachian valve and an atrial septal defect.