Endobronchial polyposis following smoke inhalation

A 50-year-old fireman was found to have multiple endobronchial polyps when investigated for hemoptysis two months after acute thermal inhalation injury. Biopsy was obtained and the histology demonstrated benign granulation tissue. The polyps spontaneously regressed, without specific treatment, six months after the accident. Tracheal bronchial polyposis appears to be another complication of heat and smoke inhalation.

Coronary circulatory dynamics before and after successful coronary angioplasty

The hypothesis that successful percutaneous transluminal coronary angioplasty restores normal coronary circulatory dynamics was tested. Regional coronary blood flow, myocardial oxygen consumption and lactate extraction were measured at rest and during sustained pacing tachycardia. Before angioplasty, tachycardia stress was associated with an attenuated blood flow and oxygen consumption response and the induction of anaerobic metabolism. After successful angioplasty, blood flow and myocardial oxygen consumption increased during tachycardia stress and aerobic metabolism was sustained. The influence of basal alpha-adrenergic tone in modifying the time course of blood flow response to abrupt pacing was also assessed. Patients with normal coronary arteries demonstrated delayed increase in blood flow after alpha-adrenergic blockade. Alpha-adrenergic blockade did not affect the time course of blood flow response in patients with coronary artery disease, suggesting that alpha-adrenergic tone was chronically withdrawn. In patients undergoing coronary angioplasty, flow response before angioplasty was delayed, consistent with withdrawal of basal alpha-adrenergic tone. After coronary angioplasty, a brisk flow response was observed, indicating that basal alpha-adrenergic tone had been restored. Thus, successful coronary angioplasty restores the normal responsiveness of the coronary circulation.

Percutaneous transluminal coronary angioplasty: report of complications from the National Heart, Lung, and Blood Institute PTCA Registry

The complications reported in the first 1500 patients enrolled in the National Heart, Lung, and Blood Institute Percutaneous Transluminal Coronary Angioplasty (PTCA) Registry are analyzed. Data were contributed from 73 centers between September 1977 and April 1981. PTCA was successful in 63% of attempts. Five hundred forty-three in-hospital complications occurred in 314 patients (21%). The most frequent complications were prolonged angina in 121, myocardial infarction (MI) in 72, and coronary occlusion in 70. One hundred thirty-eight patients (9.2%) had major complications (MI, emergency surgery or in-hospital death). One hundred two patients (6.8%) required emergency surgery, usually for coronary dissection or coronary occlusion. Sixteen patients (1.1%) died in-hospital; the mortality rate was 0.85% in patients with one-vessel disease and 1.9% in those with multivessel disease. The mortality rate was significantly higher in patients who had had bypass surgery (p less than 0.001). Nonfatal complications were significantly influenced by the presence of unstable angina (p less than 0.001) and initial lesion severity greater than 90% diameter stenosis (p less than 0.001). This report delineates and assesses the complications encountered with PTCA during its initial 3 1/2-year clinical experience. These results support the relative safety of PTCA as a method of nonsurgical myocardial revascularization in carefully selected patients.

The effect of intraaortic balloon counterpulsation on regional myocardial blood flow and oxygen consumption in the presence of coronary artery stenosis in patients with unstable angina

To determine whether a reduction in myocardial oxygen demand or an increase in coronary blood flow or both are responsible for the salutory effect of intraaortic balloon counterpulsation (IABP) in relieving medically refractory angina, we assessed these variables in six patients in whom IABP was required for relief of myocardial ischemia. IABP decreased the rate-pressure product and aortic end-diastolic pressure, and the peak systolic aortic pressure and regional myocardial oxygen consumption declined in all but one patient. Peak and mean aortic diastolic pressures increased. Changes in regional coronary blood flow paralleled changes in peak systolic aortic pressure (r = 0.92, p less than 0.007). Thus, relief of angina during IABP could not be ascribed to an increase in regional coronary blood flow. Reduction of myocardial oxygen consumption is the most likely mechanism by which IABP relieves myocardial ischemia in patients with unstable angina pectoris.

Percutaneous transluminal coronary angioplasty: report from the Registry of the National Heart, Lung, and Blood Institute

Data have been collected from 34 centers in the United States and Europe performing percutaneous transluminal coronary angioplasty since September 1977. The procedure was carried out in 631 patients, with an average age of 51 years (range 23 to 76), of whom 80 percent had single vessel coronary disease, 17 percent had double or triple vessel disease and 3 percent had stenosis of the left main coronary artery. Coronary angioplasty was successful (greater than 20 percent decrease of coronary stenosis) in 59 percent of the stenosed arteries. The mean degree of stenosis was reduced from 83 to 31 percent. Emergency coronary bypass operation was required in 40 patients (6 percent). Myocardial infarction occurred in 29 patients (4 percent). In-hospital death occurred in six patients (1 percent), three with single vessel and three with multivessel disease. Ninety-one patients have been followed up for at least 1 year after coronary angioplasty. Of the 65 patients with an initially successful angioplasty, 83 percent were in improved condition compared with their status before angioplasty. Thus, the initial satisfactory results obtained in a few centers have now been confirmed in many centers using transluminal coronary angioplasty.

Percutaneous vs surgical placement of intra-aortic balloon assist

Fifty-three patients required IABP over a one-year period. The type of insertion (percutaneous vs surgical) was used randomly. The hemodynamic effect, complication rate, and inability to insert the balloon were similar in both groups. Besides less trauma and cost-effectiveness, the most important advantage of percutaneous over surgical balloon insertion is shorter time interval between decision and insertion which thus allows faster stabilization of ischemic heart patients.

Evaluation of the role of coronary angioplasty in patients with unstable angina pectoris

Seventeen patients presenting with unstable angina pectoris underwent percutaneous transluminal coronary angioplasty (PTCA). Despite vigorous medical therapy, all patients were disabled with 10 experiencing refractory in-hospital angina. PTCA was judged successful in 13 patients and resulted in decreased coronary diameter narrowing from 80 +/- 16% to 34 +/- 13% and reduced transstenotic pressure gradient from 69 +/- 13 to 23 +/- 12 mm Hg. Regional coronary blood flow (CBF) and myocardial metabolism were assessed at rest and during pacing tachycardia in six patients with left anterior descending coronary stenosis. Prior to PTCA, neither regional CBF increased nor coronary vascular resistance declined during rapid pacing; myocardial lactate extraction fell, indicating a shift from aerobic to anerobic metabolism. Following PTCA, however, rapid pacing resulted in increased regional CBF, decreased coronary vascular resistance, and preservation of aerobic metabolism. Following PTCA, successfully dilated patients demonstrated marked relief of angina symptoms, increase in functional capacity, and objective exercise ECG and thallium scintigraphic evidence of relief of previously ischemic myocardium. This investigation demonstrates that PTCA, when combined with medical therapy, can be performed safely and successfully in selected patients who present with otherwise refractory unstable angina, and indicates the procedure deserves further study as a therapeutic alternative in this condition.

Responsiveness of the coronary circulation to brief vs sustained alpha-adrenergic stimulation

The effects of brief and sustained pharmacologic alpha-adrenergic stimulation on the coronary arterial circulation were compared in awake pigs. Phenylephrine was administered into the left anterior descending coronary artery (LAD) either as a bolus (eight pigs) or as a 15-minute infusion (eight pigs), with myocardial blood flow measured by the radioactive microsphere technique. Flow in the distribution in the LAD was compared with flow in myocardium perfused by the left circumflex coronary artery (LCF) as the ratio LAD/LCF. This technique corrects for systemic factors capable of modifying oxygen demand, and hence myocardial blood flow, in both zones. After a phenylephrine bolus (50-100 microgram), LAD/LCF fell significantly, whereas no change was observed after the sustained infusion (5-10 and 50-100 microgram/min). Four additional pigs were pretreated with i.v. adenosine to raise myocardial blood flow in excess of demand before sustained stimulation. In this setting LAD/LCF fell significantly during the sustained phenylephrine infusion. Brief alpha-adrenergic stimulation could overcome normal flow regulatory mechanisms and resulted in constriction of coronary resistance vessels. Such changes did not occur after sustained stimulation and suggest an ability of the coronary circulation to offset chronic vasoconstrictive effects. When the myocardium is overperfused, sustained alpha-adrenergic stimulation does not jeopardize myocardial oxygenation and its vasoconstriction potential is unmasked.

Restoration of normal coronary hemodynamics and myocardial metabolism after percutaneous transluminal coronary angioplasty

Regional coronary blood flow and myocardial metabolism were evaluated in a patient who underwent percutaneous transluminal coronary angioplasty (PTCA). Angioplasty increased coronary luminal diameter and reduced trans-stenotic gradient. Before PTCA, angina pectoris developed during sustained rapid atrial pacing and was associated with abnormal lactate metabolism and a mild increase in coronary flow and myocardial oxygen consumption. After PTCA, angina was absent during pacing and lactate extraction was preserved. Coronary flow and oxygen consumption were increased to a greater degree than before PTCA. The temporal response of changes in coronary blood flow due to an abrupt increase in heart rate was also evaluated. Floow reached peak value more rapidly after PTCA. These observations suggest that PTCA may result in improved regional coronary blood flow and restoration of normal flow regulatory mechanism and myocardial metabolism.

Cardiac complications of polymyositis

We report 3 cases of polymyositis, confirmed by enzyme assay and muscle biopsy, complicated by serious cardiac disease. They showed progressive fascicular block, despite immunosuppressive therapy sufficient to control the skeletal muscle disease, culminating in complete heart block with syncope, requiring the implantation of a pacemaker. In addition, all 3 showed echocardiographic evidence of dilated cardiomyopathy.

Refractory ergonovine-induced coronary vasospasm: importance of intracoronary nitroglycerin

Recent experience has suggested that the ergonovine maleate test is a safe procedure for the diagnosis of variant angina pectoris, because ergonovine-induced coronary vasospasm has generally been reversible by sublingual nitroglycerin. This report describes five cases of ergonovine-induced coronary vasospasm that were refractory to sublingual nitroglycerin. Four of these patients had cardiac arrest. In two patients the vasospasm was responsive to intracoronary nitroglycerin administration. Three patients died as a reuslt of the test. The two survivors differed from the nonsurvivors in the total dose or ergonovine given (0.1 and 0.15 mg versus 0.17, 0.3 and 0.3 mg, respectively) and in the method of administration of ergonovine. The survivors were given serial doses of 0.05 mg each whereas the three nonsurvivors received either larger initial doses (0.1 followed by 0.07 mg) or progressive incremental doses (0.05, 0.1 and 0.15 mg serially). Sublingual nitroglycerin, given to all five patients, and intravenous nitroglycerin, given to three of the five, were ineffective in reversing vasospasm. Intracoronary nitroglycerin favorably altered the course of the survivors. Thus, the ergonovine maleate test is not benign and may cause severe coronary vasospasm that is unresponsive to sublingual and intravenous nitroglycerin, but may be reversed by intracoronary nitroglycerin.

Clinical, angiographic and hemodynamic characteristics of patients with a strongly positive exercise test

To determine the clinical, angiographic and hemodynamic characteristics of patients with a strongly positive exercise test, 37 subjects demonstrating greater than or equal to 3 mm S-T segment depression were identified among 892 consecutive diagnostic treadmill evaluations. Typical angina by history was present in 78%. 30 patients (81%) had a normal resting electrocardiogram. The strongly positive exercise response was elicited at < 90% of the predicted maximal heart rate in 31 patients (84%). 20% of patients did not experience angina during testing. 20 patients underwent cardiac catheterization. All 20 demonstrated multivessel disease and each had significant stenosis of either the left main (25%) or left anterior descending (95%) coronary artery. Left ventricular function was well preserved.

Effective treatment of supraventricular arrhythmias with acebutolol

To evaluate the antiarrhythmic efficacy of the new beta adrenergic blocking agent acebutolol, 15 monitored patients with supraventricular arrhythmias received, in double-blind fashion, an intravenous infusion of either acebutolol or saline solution after a control period. Patients treated with saline solution demonstrated no change (P greater than 0.05) in heart rate or arterial blood pressure or conversion to sinus rhythm. After administration of acebutolol, significant (P less than 0.05) reductions in heart rate were noted at 5 minutes. Peak reduction occurred at 10 to 30 minutes and correlated with maximal acebutolol plasma concentrations, antiarrhythmic activity persisted for 24 hours. Mild reductions in systolic blood pressure were observed in the majority of patients. Two patients with atrial fibrillation and one with multifocal atrial tachycardia had conversion to sinus rhythm. Frequent premature atrial complexes noted in one patient were greatly suppressed after administration of the drug. In the nine patients with clinical evidence of chronic obstructive lung disease acebutolol was well tolerated. Adverse reactions were limited to transient dyspnea in one patient with prior heart failure and a decrease in systolic blood pressure to less than 90 mm Hg in three patients who remained asymptomatic. In the patients studied, acebutolol was an effective agent for the treatment of supraventricular arrhythmias and appeared to be of special value in those with chronic obstructive lung disease.

Significance of the negative exercise test in evaluation of patients with chest pain

Fifty-three patients with chest pain and a negative exercise test at greater than 85% predicted maximal heart rate underwent coronary arteriography. Twenty-one patients (40%) had significant luminal narrowing in one or two vessels. No patient had left main disease. Pathologic electrocardiographic Q waves were present in only coronary heart disease patients (p less than 0.001). There was no difference (p greater than 0.05) in prevalence of T wave abnormalities, chest pain or ventricular beats during exercise in patients with or without coronary disease. Analysis of sex distribution revealed that typical angina pectoris was uncommon in the women (p less than 0.001) and all twenty-one coronary patients were men (p less than 0.001). We conclude that in patients with chest pain and a negative exercise test, three vessel or left main coronary artery disease is unlikely. Also, women with atypical chest pain and a negative exercise test are unlikely to have a fixed coronary obstruction.

Acute coronary occlusion in the pig: effect of nitroglycerin on regional myocardial blood flow

Myocardial blood flow was studied in 10 closed chest, anesthetized pigs after an acute balloon catheter occlusion of the left anterior descending coronary artery. With use of radioactive microspheres (15 mu), myocardial blood flow was measured before and during an intravenous nitroglycerin infusion and during a combined nitroglycerin-phenylephrine infusion. A significant zone of ischemis (myocardial blood flow less than 50 percent of normal zone flow) was produced by the occlusion and involved 15 percent of the combined left ventricular and interventricular septal mass. More than 50 percent of this ischemic zone was intensely ischemic (myocardial blood flow 0 to 3 percent of normal). Nitroglycerin resulted in a 20 to 30 mm Hg decrease in systolic blood pressure. Myocardial blood flow was unchanged in intensely ischemic areas but varied directly with the product of heart rate and systolic blood pressure in the moderately ischemic area (myocardial blood flow 26 to 50 percent of normal). S-T segment elevation was significantly increased during nitroglycerin infusion and returned to control level with the added infusion of phenylephrine sufficient to restore the systemic blood pressure to prenitroglycerin values. No improvement in ischemic zone perfusion could be demonstrated during the infusion of nitroglycerin alone or with phenylephrine. The endocardial-epicardial flow ratio in moderately ischemic areas was slightly lower than the normal zone flow ratio and decreased slightly during infusion of nitroglycerin. With the addition of phenylephrine, the ratios rose slightly and no longer differed from prenitroglycerin values. Blood flow distribution in acutely ischemic pig myocardium differs considerably from that observed in the dog. Nitroglycerin was not shown to have any beneficial effects with or without its relative hypotensive effect. More extensive study in animal models other than the dog is needed.

Mechanical failure causing current leakage with unipolar pacemakers: significance and detection

Pacemaker malfunction caused by mechanical failure at the site of electrode generator connection has been observed in 5 patients fitted with unipolar pacemakers. Intermittent failure to capture occurred in one patient. The fault was the same in each case and resulted from fracture of a plastic screw designed to hold an insulating cap in place over the electrode generator connection. Changes in impulse amplitude, relative pacing threshold, and distortion of the shape of the pacemaker impulse (overshoot of the leading and trailing limbs and prolongation of the plateau length) occurred in each case, and are helpful in making the diagnosis. In contrast no significant change occurred in the frontal plane axis of the pacemaker impulse. It is concluded that current leaks in unipolar pacemakers can be of sufficient magnitude to cause failure to capture. Early detection is important and is best achieved by examination of the pacemaker signal for amplitude and shape, and assessment of pacing threshold where possible.

24-hour ambulatory electrocardiographic monitoring on a regional basis

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Hemodynamic assessment of oral peripheral vasodilator therapy in chronic congestive heart failure: prolonged effectiveness of isosorbide dinitrate

To evaluate the effectiveness of oral vasodilator therapy in chronic congestive heart failure, 20 mg of isosorbide dinitrate or placebo was administered orally in double-blind fashion to 25 patients with congestive heart failure. In 15 patients receiving isosorbide dinitrate, pulmonary arterial wedge pressure decreased 5 minutes to 5 hours after drug administration; the peak reduction was observed at 1 hour (from 23 to 14 mm Hg; P less than 0.001). Wedge pressure decreased to normal (12 mm Hg or less) in 8 of the 15 patients (Group I) but remained greater than 12 mm Hg in 7 (Group II). Reductions in mean systemic arterial pressure, systemic vascular resistance and pressure-time per minute also occurred. Indexes of pump output were unchanged in the 15 who received isosorbide dinitrate but tended to decrease slightly in Group I. Stroke index (from 23 to 26 cc/m2) and stroke work index (from 21.4 to 24.1 g-m/m2) increased slightly but significantly (P less than 0.05) in Group II. Thus the prinicpal hemodynamic action of isorbide dinitrate is marked and sustained reduction in left ventricular filling pressure without pronounced effect on cardiac output. This agent should be used in congestive heart failure primarily for relief of congestive symptoms.

Muscle potentials simulating pacemaker malfunction

Interference spikes were noted on the electrocardiogram of a patient with an implanted demand pacemaker. Runaway malfunction was suspected and the generator replaced. Subsequent investigation showec that the interference originated from fasciculation in the left leg caused by underlying neuromuscular disease. Skeletal muscle potentials can produce an electrocardiographic appearance closely resembling 'runaway' pacemaker. Such abnormalities should prompt a search for occult neuromuscular disease.

Pharmacological mechanisms for left ventricular unloading in clinical congestive heart failure. Differential effects of nitroprusside, phentolamine, and nitroglycerin on cardiac function and peripheral circulation

We compared cardiocirculatory actions of the commonly employed systemic vasodilators, intravenous (iv) nitroprusside (NP), iv phentolamine (PH), and sublingual nitroglycerin (NTG), causing left ventricular (LV) unloading in 29 chronic coronary subjects with congestive failure to determine whether they produce disparate responses in LV function by different relaxing actions on systemic resistance and capacitance beds. Each drug equally lowered systemic arterial pressures to a small extent, whereas heart rate rose slightly with NTG. Cardiac catheterization showed a decline in end-diastolic pressure with NTG (19 to 8 mm Hg) which was greater (P less than 0.05) than with NP and PH (21 to 11). Cardiac index increased (P less than 0.05) during NP (2.68 to 2.93 liters/min per m2) and PH (2.60 to 3.02) but was unchanged (2.83) by NTG. Stroke work increased with PH, ejection fraction rose with NP and PH, and mean ejection rate increased with each, whereas pressure-time per minute fell and end-diastolic volume decreased with each agent. Total systemic vascular resistance declined (P less than 0.001) during NP and PH (1,475 to 1,200 dynes sec cm-5) but was unchanged (1,487) by NTG. Plethysmographically, forearm vascular resistance (FVR) decreased (P less than 0.01) with NP and PH (61.6 to 39.1 mm Hg/ml per 100 g/min) but not (52.4) by NTG. The decreases in venous tone (VT) with NTG (18.2 to 9.3 mm Hg/ml) and NP (18.5 to 9.8) were greater (P less than 0.05) than with PH (18.8 to 13.1) FVR/VT percent changes of 0.96, 1.62, and 0.53 with NP, PH, and NTG indicated balanced systemic arteriolovenous relaxation by iv NP, greater arteriolar dilation with iv PH, and predominant venous dilation by sublingual NTG. Thus, vasodilators produce disparate modifications of LV function by their differing alterations of preload and impedance, which are dependent upon relative extents of relaxation of systemic resistance and capacitance vessels characteristic of each agent as used clinically.

Detection of somatic muscle fasciculation on electrocardiograms

Small discrete spikes appearing on the electrocardiogram (ECG) of a man with a pacemaker turned out to be fasciculation potentials picked up from leg muscles. To find out how common these spikes were all routine ECGs made in one month were reviewed. Spike potentials were found in six patients, and in each case they originated from somatic musculature. Spikes could nearly always be detected on ECGs that were recorded subsequently in patients known to have lower motor neurone lesions that produced fasciculation. Thus the presence of these fasciculation spikes may suggest underlying neuromuscular disease; this possibility should be recognised by those who record ECGs so that the spikes are not suppressed by overuse of the filter.

Functional significance of coronary collateral vessels in patients with acute myocardial infarction: relation to pump performance, cardiogenic shock and survival

In 20 patients with acute myocardial infarction requiring emergency left heart catheterization and coronary arteriography, ventricular function and clinical course were related to collateral vessels supplying the infarcted area. The major coronary artery to the infarcted region was severely obstructed in all patients. Patients with adequate collateral vessels (Group I, no. = 6) and those with no or inadequate collateral channels (Group II, no. = 14) had similar findings with respect to age, site of infarction, prevalence of prior infarction and presence of multivessel disease. However, there were significant differences between Groups I and II in left ventricular end-diastolic pressure (13 versus 30 mm Hg), cardiac index (3.05 versus 2.04 liters/min per m2), stroke work index (45 versus 13 g-m/m2), ejection fraction (42 versus 20 percent) and area of dyssynergy (14 versus 47 percent). Moreover, in Group I all patients survived and none had cardiogenic shock, whereas in Group II 10 of 14 patients had shock and 8 of 14 died. The rapidity of vessel obstruction appeared to influence collateralization since infarction was preceded by angina pectoris more frequently in Group I than in Group II. These results indicate that well functioning anastomotic channels to the distal trunk of the blocked coronary artery may afford some protection of pump function and improve the prognosis in acute myocardial infarction.

Selective versus non-selective His bundle pacing

His bundle pacing was achieved in 10 anaesthetized open chest dogs by stimulation from bipolar electrode catheters positioned in the aortic root and right heart. Recordings were taken directly through plunge wires from the right atrium, high ventricular septum, and epicardial sites on the right and left ventricles. Six types of response were seen during A-V junctional stimulation: (1) low atrial pacing; (2) combined atrial and His bundle pacing; (3) His bundle pacing; (4) combined atrial, ventricular septal, and His bundle pacing; (5) combined septal and His bundle pacing; and (6) ventricular pacing. Pacing of the His bundle in combination with the atrium and/or ventricular septum is designated as non-selective, whereas stimulation of the His bundle alone is considered selective pacing. Non-selective His bundle pacing can be recognized from the surface leads by changes in onset and amplitude of the QRS with appreciable T-wave alterations. Although electrode position was an important determinant of the type of pacing achieved, a variety of patterns of stimulation resulted from variation in the modalities of the pacing stimulus, ie, polarity, intensity, and duration. Unless these factors are considered, selective His bundle pacing may not be achieved.

Hemodynamic effects of nitroglycerin in acute myocardial infarction

Nitroglycerin (NTG) has recently been suggested to decrease myocardial ischemia and enhance cardiac pump function during acute myocardial infarction (AMI). To evaluate the sublingual agnet in this condition, the hemodynamic effects of 0.4 mg NTG administered to 16 supine patients during the first 72 hours of AMI were determined serially 5, 10 to 15, and 20 to 30 minutes post-NTG. Data were evaluated for the entire group, as well as for six patients with normal pulmonary artery wedge pressure (PAW) (less than or equal to 12 mm Hg; mean 7) who formed group I and for ten patients with elevated PAW (greater than 12 MM Hg; mean 19) who comprised group II. In the 16 patients, NTG resulted in significant decreases in PAW (14 TO 7 MM Hg; P less than .01), mean systemic arterial pressure (MAP) (95 TO 82 MM Hg; P less than .01), cardiac index (CI) (1.79 TO 1.46 L/min/m-2; P less than .02), stroke index (SI) (24 TO 18 CC/M-2; P less than .01) and stroke work index (SWI) (27 TO 20 GM TIMES M/M-2; P less than .01). These alterations were significant in both subgroups, with the decline in PAW greater (P less than .05), while there was no change in group II. There was no significant change in total peripheral vascular resistance (TPVR) for the entire group or in the two subgroups. This study demonstrates that, regardless of initial left ventricular filling pressure, sublingual NTG given in the acute phase of AMI results in rapid fall in PAW, concomitant with decreases in systemic blood pressure, cardiac output and SWI, without changes in TPVR and with little or no effect on heart rate. Since TPVR was unaltered, the decline in MAP was due to fall in cardiac output. Thus, the principal action of sublingual NTG in AMI appears to be systemic venodilation with consequent reduction of ventricular preload. This effect is translated into decline ofpump output even in patients with high initial filling pressures. Although NTG may rapidly relieve pulmonary congestion and lower myocardial oxygen consumption, use of the agent sublingually is limited in AMI because these salutary effects are accomppanied by potentially deleterious fall in cardiac output and systemic blood pressure.

The pathophysiology of malignant ventricular arrhythmias during acute myocardial ischemia

In 20 anesthetized open-chest dogs, epicardial electrograms were recorded from ischemic and nonischemic zones of the left ventricle during acute occlusion of the left anterior descending artery. The average time to onset of ventricular tachycardia during atrial pacing (150-200 beats/min) was 4 min, 18 sec. In 18 dogs, ventricular ectopic beats were induced in normal and ischemic zones after every tenth atrial stimulus. Those induced in the ischemic zone consistently caused ventricular tachycardia earlier (mean: 3 min, 22 sec) than those in the normal zone (mean: 4 min, 11 sec) ( P < 0.01). This arrhythmia, whether spontaneous or induced, always followed the complex which demonstrated the greatest delay of the ischemic zone potential and increased ventricular activation time. Ventricular tachycardia was repeatedly produced by ectopic beats with late diastolic coupling. Analysis of the episodes of tachycardia leading to fibrillation revealed a progressive increase in the ventricular activation time of the successive beats, whereas in those self-terminating episodes ventricular activation time progressively decreased. These data suggest that the major determinant of malignant ventricular arrhythmias in acute ischemia may be the related abnormalities of ventricular activation rather than the coupling of the premature ectopic beats.

The pathophysiology of tachycardia-dependent paroxysmal atrioventricular block after acute myocardial ischemia. Experimental and clinical observations

The pathophysiology of paroxysmal A-V block (PAVB) was studied in 20 anesthetized dogs after ligation of the anterior septal artery. Simultaneous recording of leads II and aV R , as well as intracardiac recordings from the His bundle (Hb) and both bundle branches, were monitored. In 18 of 20 experiments, PAVB was localized in the Hb. In all experiments, PAVB occurred subsequent to Mobitz type II A-V block. In eight experiments, PAVB occurred spontaneously during sinus rhythm and was preceded by a period of Wenckebach periodicity superimposed upon a 2:1 A-V block. Vagal-induced slowing of the sinus rate resulted in immediate resumption of 1:1 A-V conduction. In 18 experiments, PAVB was induced by atrial pacing at a critical heart rate in each case (180-300 beats/min). Evidence is presented that A-V conduction was consistently blocked below a critical H-H interval. Slowing the pacing rate, termination of pacinig or increasing the pacing rate until physiological A-V nodal block occurred, all could result in a longer H-H interval and immediate resumption of A-V conduction. When the critical heart rate for PAVB was maintained, a slow idioventricular escape rhythm occurred.

Five patients who developed PAVB after acute myocardial ischemia are also reported providing the clinical counterpart for the experimental observations. In all five cases, PAVB occurred on acceleration of the sinoatrial rate (105-140 beats/min) which was spontaneous in two and induced by drugs given for varied therapeutic indications in three (isoprenaline in two and atropine sulfate in one). In all five, PAVB was associated with Mobitz type II and/or 2:1 A-V block. These experimental and clinical observations suggest that PAVB after acute myocardial ischemia appears to be due to a tachycardia-dependent repetitive concealed conduction in the ischemic His-Purkinje system, probably mainly in the Hb. The clinical observations point out potential consequences of a rapid atrial rate in patients with acute myrocarcial ischemia and type II A-V block.

The efficacy of antiarrhythmic agents during acute myocardial ischemia and the role of heart rate

The influence of lidocaine, procaine amide, and propranolol on ventricular arrhythmias during acute myocardial ischemia in the dog was examined. Ischemic zone epicardial (IZE) activation delay and the time of onset of ventricular tachycardia (VT t ) were studied. Progressive IZE delay always preceded ventricular tachycardia (VT). Ventricular tachycardia occurred when IZE delay extended into the T wave of the standard electrocardiogram but areas of ischemic epicardium were found in which activation delayed beyond the T wave. Fast heart rates during acute ischemia were associated with an accelerated time course of IZE delay and early VT. Slow heart rates resulted in minimal IZE delay and delayed onset or absence of VT. Sympathectomized dogs with heart rates 32% slower than normal dogs did not develop significant IZE delay or VT during ischemia. When heart rates were increased by atrial pacing, these dogs behaved in the same fashion as the normal dogs with respect to IZE delay and VT t . Lidocaine was found to hasten the time course of IZE delay but to have no significant effect on VT t . Procaine amide did not influence IZE delay nor VT t during ischemia. Propranolol slowed the mean heart rate by 20% and appeared to protect against arrhythmia. When the heart rate (115 ± 10 beats/min; mean ± standard deviation) was increased by atrial pacing (184 ± 9 beats/min), propranolol did not significantly influence IZE delay or VT t as compared to the untreated controls. The clinical counterpart of our experiments during acute ischemia may relate to the prehospitalization phase of myocardial infarction.

Long-term treatment of refractory sypraventricular tachycardia by patient-controlled inductive atrial pacing

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Preferences for black skin among Negro adults

24 black Ss, age 15 to 25, 35 to 45, 55 to 65 yr., were required to choose a real and ideal face from 11 faces which differed in skin color and attribute desirable and undesirable behavioral attributes to 20 figures, 10 of which were Negro. Analyses of the former task showed neither a significant preference on the part of all Ss for dark skin colors nor an increasing tendency for older Ss to prefer light skin; analyses of the latter task also indicated that across all age groups there was no preference for dark skin. However, Ss in the youngest age group attributed significantly more positive behavioral attributes to black skin than Ss in the older age categories.

Supernormal phase of AV conduction. A study during heart block and endocardial pacing

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Combined axillary plexus block and basal sedation for cardiac catheterization in young children

A technique for the management of cardiac catheterization in children is described which combines axillary plexus block with basal sedation. The technique offers a quiet still arm with pronounced vasodilatation, permitting the use of larger catheters than usual, making sampling easier, and giving undamped pressure records. These factors, together with the absence of venospasm, make catheterization of an arm vein in young chīldren a feasible proposition; in addition arterial sampling via the brachial artery may be performed without further inconvenience to the child.

Multiple emboli from left ventricular myxoma

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