Lidocaine-induced cardiac rate changes in atrial fibrillation and atrial flutter

To assess atrial and ventricular rate changes after lidocaine injection, 18 atrial flutter patients and 35 atrial fibrillation patients were given intravenous lidocaine, mean dose 100 mg. Continuous electrocardiographic recording for 5 minutes before and at least 10 minutes after lidocaine injection was used to determine rate changes. The atrial flutter rate decreased after lidocaine in 17 of 18 patients (94 per cent), mean maximal decrease 27 beats/minute. The ventricular rate response in atrial flutter was variable but in three patients increased 21, 27, and 47 beats/minute respectively (P less than 0.001). In atrial fibrillation, the mean ventricular rate after rapid lidocaine injection increased six beats/minute (P less than 0.01). In three of 35 atrial fibrillation patients (9 per cent), the ventricular rate increase was greater than 20 beats/minute (P less than 0.001), and in two patients (6 per cent), the ventricular rate increase was associated with potentially serious clinical events. Lidocaine-induced ventricular rate increases are common in atrial flutter and fibrillation, particularly in patients who are also receiving quinidine.     

Echocardiographic features of experimental left atrial tumor

An experimental technique for simulating left atrial tumors and their echocardiographic features is described. The echocardiographic demonstration of tumor movement between atrium and ventricle was noted in all cases and reliably detected the tumor. A normal E-to-F slope could be seen in the presence of a tumor. A notch or plateau was at times found on the AC component of the mitral valve echo and its hemodynamic implications are discussed. The controversy concerning whether blood or tumor enters the left ventricle first during diastole is resolved in favor of the former. The demonstration of tumor, mitral leaflet, and ventricular-septal contact provides a possible explanation for the presence of mitral valve lesions and tumor emboli in left atrial myxoma.     

Limitation of the surface electrocardiogram in diagnosis of atrial arrhythmias. Further observations on dissimilar atrial rhythms.

Electrophysiologic studies with recordings of multiple intracavitary electrograms were performed in two patients with atrial dysrhythmias. In Case 1 the arrhythmic pattern in the surface electrocardiogram resembled atrial flutter. Electrophysiologic studies revealed the arrhythmia to be paroxysmal left atrial tachycardia, with separation of left and right atrial components of the P wave by an isoelectric period secondary to marked interatrial conduction delay. In Case 2 the surface electrocardiogram indicated paroxysmal atrial tachycardia with block. Electrophysiologic studies revealed right atrial standstill with atrial inexcitability and two dissimilar rhythms involving the left atrium. The electrocardiograms did not accurately reflect atrial arrhythmias in these two patients and only multiple direct recordings permitted the correct diagnoses. New electrophysiologic observations concerning intraatrial block and dissimilar atrial rhythms are presented.     

Assessment of echocardiographic left atrial enlargement in patients with atrial fibrillation. An electrovectorcardiographic study.

Standard 12 lead electrocardiograms (ECG) and timed Frank vectorcardiograms (VCG) were recorded in 53 subjects with atrial fibrillation. Thirty-eight patients had echocardiographically documented left atrial enlargement (greater than 4.0 cm) and 15 patients had normal atrial dimensions. The magnitude of the largest "f" wave component during an average cycle length was measured in lead V1 of the ECG and the horizontal plane VCG running loop. Relative sensitivies for detection of left atrial enlargement were: VCG, 25/38 (66%) and ECG 10/38 (26%). An enlarged left atrial internal dimension was diagnosed by the VCG alone in 21 of the 38 subjects (55%). In the group of 15 patients with normal echocardiographic left atrial internal dimensions the prevalence of ECG false positive diagnosis for enlarged left atrial size was 6% in contrast with 0% for the VCG. It is concluded that: 1) the timed Frank VCG is superior to the ECG for the detection of echocardiographically demonstrable left atrial enlargement; 2) the timed VCG and ECG represent complementary techniques for identifying patients with abnormally large left atria; and 3) large fibrillatory waves are rarely observed on the ECG or VCG when the left atrial internal dimension is echographically normal.     

Effect of inotropic stimulation on left atrial appendage function in atrial myopathy of chronic atrial fibrillation

Atrial fibrillation (AF) leads to remodeling of the left atrium (LA) and left atrial appendage (LAA), resulting in atrial myopathy. Reduced LA and LAA function in chronic AF leads to thrombus formation and spontaneous echo contrast (SEC). The effect of inotropic stimulation on LAA function in patients with chronic AF is unknown. LAA emptying velocity (LAAEV) and maximal LAA area at baseline and after dobutamine were measured by transesophageal echocardiography in 14 subjects in normal sinus rhythm (NSR) and 6 subjects in AF. SEC in the LA was assessed before and after dobutamine. LAAEV increased significantly in both groups. However, the LAAEV at peak dobutamine in patients with AF remained significantly lower than the baseline LAAEV in patients who were in NSR (P = 0.009). Maximal LAA area decreased significantly with dobutamine in both groups, but LAA area at peak dose of dobutamine in patients with AF remained greater than baseline area in those in NSR (P = 0.01). Despite the increase in LAAEV, SEC improved in only two of five patients. We conclude that during AF, the LAA responds to inotropic stimulation with only a modest improvement in function.     

Echocardiographic correlates of atrial contraction in normal and abnormal atrial rhythm

Echocardiographic manifestations of normal atrial contraction on the left ventricular posterior wall (LVPW), ventricular septum (VS), right ventricular anterior wall (RVAW), and the aortic root have not been described previously in detail. In 150 consecutive echocardiograms recorded from patients in normal sinus rhythm, we have been able to find correlates of normal atrial contraction (A waves) on the LVPW in 130, on the VS in 95, on the RVAW in 27, and on the aortic root in 107. These waves occurred on the aortic root 0.04 0.06 sec after the onset of the P wave, and they occurred on the other cardiac structures 0.06 0.10 sec after the onset of the P wave. That these waves were due to atrial contraction was established by their close temporal relationship to the P wave in normal and abnormal atrioventricular (AV) conduction and by their absence whenever the QRS complex was not preceded by a P wave. First-degree AV block was associated with “premature” mitral closure. Premature atrial contractions produced definite A waves on the aortic root, but less distinct waves on the other structures. These echocardiographic correlates of atrial contraction provide another noninvasive means of assessing the atrial contribution to ventricular filling.

Echocardiographic study of ten patients in atrial flutter showed that atrial flutter contractions produced regular undulations on the mitral valve leaflets, tricuspid valve leaflets, left ventricular posterior wall, ventricular septum, aortic root and cusps, and the anterior and posterior left atrial wall.

Echocardiographic observations made in 40 patients in atrial fibrillation frequently showed undulations on the mitral and tricuspid valves, aortic root, pulmonary valve cusp, and left atrial anterior wall. In some instances, the diastolic undulations on the mitral valve leaflets showed only minimal variations in amplitude and frequency even though the simultaneously recorded electrocardiogram showed marked irregularity of amplitude and frequency of atrial undulations.     

The echocardiogram in left atrial myxoma

A case of left atrial myxoma is described in which the echocardiogram provided the clue to the diagnosis. The mechanisms involved in producing a positive result are discussed. The value of the echocardiogram appears to depend upon echoes from the tumor during diastole which can be detected immediately posterior to the anterior cusp of the mitral valve. In this case the tumor was successfully removed with restoration of the normal pattern of mitral valve movement.     

Dissimilar atrial rhythms. A patient with triple right atrial rhythm

A patient with complete A-V block and atrial fibrillation was analyzed by multiple intra-atrial electrograms. Three areas were recorded in the right atrium, each of them with different electrophysiological properties: (1) persistent atrial standstill, (2) irregular atrial activity with a rate of 50/minute, and (3) fibrilloflutter waves with a rate of 450/minute. The latter were also registered in the left atrium.This case illustrates another form of dissimilar atrial rhythms, and provides additional evidence of the importance of recording multiple electrograms from each atrium in the evaluation of the atrial events in atypical atrial arrhythmias.     

Effect of atrial fibrillation on atrial blood flow in conscious dogs

This study was undertaken to examine the independent effects of atrial tachycardia, ventricular tachycardia, and atrial fibrillation (AF) on atrial and ventricular blood flow in conscious, heart-blocked dogs using radioactive microspheres. Atrial blood flow averaged 0.54 ± 0.08 ml/min/g during the control period at an atrial rate of 124 beats/min and a ventricular rate of 90 beats/min. Atrial flow increased to 0.72 ± 0.12 ml/min/g during atrial pacing at 236 beats/min, but was not significantly altered by ventricular pacing at 200 beats/min. AF at a ventricular rate of 90 beats/min resulted in atrial flow values of 0.91 ± 0.08 ml/min/g. The ratio of atrial flow to left ventricular flow during AF averaged 1.18 ± 0.08. Administration of a maximal vasodilating dose of adenosine during AF further increased atrial flow to 2.18 ± 0.16 ml/min/g. Atrial tachycardia or AF did not significantly affect ventricular blood flow. These data indicate (1) that atrial blood flow increases significantly during AF, reaching flow values per gram of tissue comparable to those of the left ventricle, and (2) that this flow is regulated by the metabolic needs of the atrial tissue and does not represent maximal vasodilation.     

Temporary atrial standstill.

Temporary atrial standstill is a relatively rare event requiring intraatrial electrogram recordings for its documentation. Previous reports have emphasized its relationship to drug intoxication, infarction, the immediate post open-heart surgery period, or the premorbid state; significant impairment of atrial excitability is usual. The occurrence of atrial standstill in the presence of intact atrial excitability suggests "electrical isolation" of the atria. The three patients we describe manifested temporary atrial standstill while maintaining atrial excitability. Diffuse conduction system disease and drug effects played a contributory role.     

Sinus nodal function in the intact dog heart evaluated by premature atrial stimulation and atrial pacing

Sinus nodal function was analyzed in 25 dogs by premature stimulation of the right atrium. The return (A_T-A_R) and post-return (A_R-A) cycles were plotted as a function of the premature cycle, and four zones were identified. Zone I (compensatory zone) was observed during the last 4.8 percent (mean value) of the sinus cycle (A-A). Zone II was observed during 43.6 to 95.2 percent (mean value) of the sinus cycle. During the latter part of zone II, A_T-A_R was nearly constant and A_R-A remained nearly equal to A-A during the last 29 percent (mean value) of the cycle. Earlier in zone II three distinct patterns of return cycle responses were observed whereas post-return cycles either remained nearly equal to A-A or showed progressive lengthening. Zone III (interpolation) was observed in 10 animals during 39.5 to 46.2 percent (mean value) of the sinus cycle. A_R-A was nearly equal to A-A in zone III. Interpolation was incomplete late and complete early in the zone. Zone IV (echo zone) was seen in another 10 animals during 40.9 to 45.3 percent (mean value) of the sinus cycle and in this zone A_R-A was greater than A-A. No significant difference in these zones was seen among the animals anesthetized with pentobarbital or alpha-chloralose, or given 6-OH-dopamine. The A_R-A was important in the analysis of these zones and appears to be essential to the interpretation of data derived from premature atrial stimulation. Responses to premature atrial stimulation through a catheter electrode positioned against the sinus nodal region compared favorably with responses to direct epicardial stimulation. After periods of continuous right atrial pacing a variety of patterns of sinus nodal depression were observed at different rates and durations of stimulation. The frequent occurrence of a short sinus escape cycle followed by the maximal pause observed during rapid pacing rates suggests sinus nodal entrance block. This may be an important factor to consider in determining an optimal pacing rate for assessing sinus nodal function.     

Prolonged atrial conduction

We describe a patient, in whom electrophysiologic study revealed a "negative" P-A interval in the His bundle electrogram, a prolonged intraatrial conduction time and a prolonged spike to the P wave interval during atrial pacing. The abnormalities were due to extensive sinuatrial disease.