Henry S. Loeb

Acute procedural results in the treatment of 30 coronary artery bifurcation lesions with a double-wire atherectomy technique for side-branch protection

Percutaneous treatment of bifurcation lesions has been consistently shown to be associated with lower acute success rates, higher initial complication rates, and an increased rate of restenosis when compared with findings in nonbifurcation lesions. Recent analysis of data from a CAVEAT subgroup suggests that directional atherectomy of bifurcation lesions can improve initial success rates and lower restenosis rates but at the cost of high complication rates. Reports from several angioplasty series document improved success rates and lower complication rates with the use of a two-wire technique to protect side branches when treating bifurcation lesions. Our experience with a two-wire atherectomy technique that uses a nitinol wire to protect important side branches is presented.

Mobitz Type II block without bundle branch block

His bundle (H) electrograms were recorded in three patients with Mobitz type II block and narrow QRS. Block was secondary to digitalis intoxication in one patient. In the second patient, who had first-degree A-V block, type II block occurred with atrial pacing at a slightly increased heart rate. In the third patient, who had corrected transposition of the great vessels, type II block occurred spontaneously. In two additional patients, block simulating type II block was noted. In one, block of single P waves occurred with carotid massage. In the other, Wenckebach periods with small increments in P-R (and P-H) intervals resembled episodes of type II block. In all five patients, block was proximal to H, suggesting the A-V node as the site of block. The conduction defects in these patients were not progressive; none of the patients needed a pacemaker.Although these mechanisms were identified in patients with narrow QRS complexes, they could occur with bundle-branch block suggesting an erroneous diagnosis of bilateral bundle-branch disease. It is concluded that His bundle recording is helpful in delineating these benign forms of block. The site of block may be a more important determinant of prognosis than the type of block.

ALTERATIONS IN TRANSMITRAL FLOW DYNAMICS IN PATIENTS WITH EARLY MITRAL VALVE CLOSURE AND AORTIC REGURGITATION

Ten patients with severe aortic regurgitation (AR) and early diastolic mitral closure demonstrated by M-mode echocardiography (group I) were compared to 10 age-matched patients with severe AR and normal timing of mitral closure to quantify the accompanying alterations in transmitral flow dynamics assessed by pulsed Doppler echocardiography. Transmitral filling period expressed as a fraction of the time available for diastolic filling was significantly shortened in group I patients relative to group II patients (0.50 +/- 0.10 vs 1.04 +/- 0.09, p < 0.001) because early mitral closure truncated transmitral filling and obliterated the atrial contribution to left ventricular filling. The rapid diastolic filling period normalized for the time available for diastolic filling was also shortened for group I patients relative to group II patients (0.49 +/- 0.11 vs 0.64 +/- 0.19; p < 0.05). Early mitral closure in group I patients was functionally incomplete because 9 of the 10 patients had diastolic mitral regurgitation, which was not detected in any patients in group II (p < 0.001). Thus the group I patients with early mitral closure and severe aortic regurgitation had truncated transmitral inflow and diastolic mitral regurgitation. These patients had higher pulmonary capillary wedge pressures (32 +/- 6 vs 11 +/- 9 mm Hg; p < 0.001) and more severe functional limitation (p < 0.001) than group II patients.

Regional changes in blood flow, extracellular potassium and conduction during myocardial ischemia and reperfusion

OBJECTIVES We postulated that ventricular arrhythmias may arise from the heterogeneous washout of ischemic metabolites. Our objective was to investigate the distribution of extracellular potassium concentration ([K+]o) during myocardial ischemia and reperfusion and to correlate this distribution with regional differences in myocardial blood flow. BACKGROUND Our previous study showed that reperfusion after a brief period of ischemia resulted in heterogeneous reflow of the ischemic myocardium. METHODS The changes in regional myocardial blood flow, midmyocardial [K+]o and electrogram duration were quantitated in 14 dogs undergoing 20 min of left anterior descending coronary artery occlusion and 1 min of reperfusion. Regional myocardial blood flow was measured by using 15-microns radioactive microspheres in 1- to 1.5-g full thickness myocardial samples. The [K+]o was measured with intramyocardial K(+)-sensitive electrodes. RESULTS During coronary occlusion, the ischemic zone exhibited a reduction in regional blood flow to 0.13 +/- 0.06 ml/g per min and increases in [K+]o to 9.3 +/- 2.6 mmol/liter and electrogram duration to 131.8 +/- 38.6% of control. Heterogeneous reduction in regional blood flow at various sites in the ischemic zone had fair correlations with variable increases in [K+]o (r = -0.70) and electrogram duration (r = -0.75). During min 1 of reperfusion, regional blood flow ranged from two to more than seven times baseline, resulting in a disorganized spatial distribution of perfusion with islands of high and low blood flows. Associated with the heterogeneous early reperfusion regional myocardial blood flow, [K+]o and electrogram duration changed at different rates toward normal. Whereas correlation between regional blood flow and [K+]o or standardized electrogram duration was fair during ischemia, this correlation was poor during early reperfusion. CONCLUSIONS Spatial heterogeneity in regional myocardial blood flow during myocardial ischemia and early reperfusion is associated with heterogeneity in [K+]o and electrophysiologic characteristics, which in turn may play an important role in the genesis of arrhythmias arising from the ischemic and reperfused myocardium.

Shock in acute myocardial infarction: evolution of physiologic therapy.

In the past 25 years the treatment of shock in myocardial infarction has evolved into a physiologic approach based on on-line measurements of hemodynamic variables. This has aided in the development of new pressor agents so that a family of pharmacologic agents is now available. Appropriate use of vasodilators and recognition and treatment of intravascular volume depletion have increased survival. Recognition and appropriate treatment of the preshock state have decreased the incidence of shock. The criteria for use of mechanical support and surgical intervention are soundly established; the use of thrombolytic therapy and balloon angioplasty for this syndrome is ready to be evaluated.

Augmentation of Cardiac Output by External Cardiac Pacing: Pacemaker‐Induced CPR

Transthoracic cardiac pacing is frequently associated with simultaneous stimulation of skeletal muscle and nerves. We describe a patient in cardiogenic shock and complete heart block in whom the associated vigorous abdominal and chest muscle contractions caused by transthoracic cardiac pacing resulted in a marked augmentation of cardiac output and systemic blood pressure via a “CPR” effect

Effect of acute pericardial tamponade on the relative contributions of systolic and diastolic pulmonary venous return: A transesophageal pulsed Doppler study

The effect of acute pericardial tamponade on pulmonary venous return was assessed by transesophageal pulsed Doppler echocardiography. In 14 open-chest anesthetized dogs peak pulmonary venous flow velocities in systole (VJ) and in diastole (VK) were measured during apnea and atrial pacing while acute tamponade was induced by intrapericardial instillation of 0.9% sodium chloride solution. Before intravascular volume expansion, induction of acute tamponade resulted in a significant decline in VK (43 +/- 17 to 19 +/- 8 cm/sec; p < 0.05) but no change in VJ or the ratio VJ/VK. After intravascular volume expansion, induction of acute tamponade resulted in significant reductions in VJ (43 +/- 9 to 29 +/- 10 cm/sec; p < 0.001) and VK (37 +/- 19 to 15 +/- 11 cm/sec; p < 0.001). The effect was disproportionately greater on VK, however, resulting in a significant increase in VJ/VK (1.51 +/- 0.84 to 2.58 +/- 1.41; p < 0.001). The disproportionate effect of acute tamponade on VK suggests that increased pericardial pressure directly constrains diastolic filling of the left atrium as a conduit to the left ventricle and that it does not decrease the systolic and diastolic phases of pulmonary venous return uniformly. Intravascular volume expansion increases cardiac output before acute tamponade, but during acute tamponade it amplifies the disproportionate impact of increased pericardial pressure on left ventricular diastolic filling as the left ventricle is constrained within the fluid-filled pericardial sac.

Various Electrocardiographic and Electrophysiologic Presentations of Normal and Abnormal Sinus Node

Electropbysiology of the Sinus Node. Differentiation of normal from abnormal sinus nodal function is frequently difficult because the electrocardiographic and electrophysiologic presentations of abnormal and normal sinus nodal function are quite diverse. The autonomic nervous system greatly influences sinus nodal function, making this differentiation even more complicated. Data obtained from the recording of sinus nodal electrogram in animals and humans have helped in elucidating changes in automaticity and conduction of the sinus node. In this review, we provide examples of rhythms related to normal and abnormal sinus nodal function. (J Cardiovasc Electrophysiol, Vol. 3, pp. 187–197, April 1992)