PubMed Health⌕ Search

Biomedical subjects

I D Malcolm

Publications and source records attributed to I D Malcolm.

17 recordsLinked to original sources
PubMed1997

Echocardiographic detection of pulmonary embolism in transit: implications for institution of thrombolytic therapy.

Right atrial or ventricular thrombi in patients with pulmonary embolism are emboli in transit and are a medical emergency because they are associated with a high mortality rate when treated conservatively with anticoagulation. The current standard therapy is less well accepted because of the risk of clot fragmentation and distal embolization. A case in which an unsuspected right ventricular thrombus was diagnosed by echocardiography is reported. This findings led to treatment with streptokinase (250,000 U, followed by 100,000 U/h for 24 h). Clinical improvement was rapidly obtained and the thrombus disappeared 10 h after the initial study. There was no complication. The case illustrates the utility of two-dimensional enchocardiography in the evaluation of patients with pulmonary embolic disease and the efficacy and safety of thrombolytic therapy in the treatment of pulmonary embolism in transit.

Echocardiography↗
PubMed1986

The use of temporary atrial electrodes to improve diagnostic capabilities with Holter monitoring after cardiac surgery.

The use of temporary atrial electrodes implanted during cardiac surgery has been advocated for diagnosis and treatment of cardiac arrhythmias in the postoperative period. We have adapted this technique to allow continuous ambulatory electrocardiographic (Holter) recording of atrial activity in patients after coronary artery surgery. The electrodes of one of the two leads of the Holter recorder were attached as a surface electrocardiographic lead, while the electrodes of the other were each attached to one of the two implanted atrial wires. The Holter record was then obtained in the usual way. A satisfactory recording of the atrial electrocardiogram and the simultaneous surface electrocardiogram was obtained in all 6 patients and resulted in improved diagnostic capabilities, specifically in differentiating supraventricular and ventricular arrhythmia. As has proven to be true in the post-myocardial infarction setting, arrhythmias that were not noted clinically despite continuous electrocardiographic monitoring were demonstrated on Holter records.

Arrhythmias, Cardiac↗
PubMed1984

Differential electrical activity of the atria during cardioplegic arrest in pigs.

To elucidate the electrical interrelationship of the atria during cardioplegic arrest, simultaneous bipolar right atrial (RA) and left atrial (LA) electrograms and myocardial temperatures of all four chambers of the heart were recorded in 10 pigs during an hour of aortic clamping. Five pigs (Group 1) underwent single venous cannulation; in 5 others (Group 2), snared double caval cannulation, RA venting, and intracavitary RA irrigation with cold saline solution were employed. Myocardial protection was provided by systemic hypothermia (28 degrees C) and intermittent intraaortic administration of cold (4 degrees C) hyperkalemic (20 mEq/L) crystalloid cardioplegic solution. Single RA cannulation was associated with sustained RA activity during cardioplegic arrest and with the warmest mean myocardial temperatures. Electrical activity was infrequent in the left atrium, which was often silent while RA impulses continued to be observed. Four Group 1 pigs exhibited high-grade RA-LA block, whereas in 2 animals completely asynchronous RA-LA electrical activity occurred. Isolated LA activity was not encountered. The combined methods used in Group 2 pigs significantly reduced mean myocardial temperatures. Both RA and LA impulses were practically abolished, and their mean durations decreased 96% and 85%, respectively. It is concluded that the pattern of electrical activity differs in the two atria during cardioplegic arrest when a single venous cannula is employed. Intracavitary RA irrigation with cold saline solution in the presence of snared caval cannulas provides improved myocardial hypothermia and effectively eliminates both RA and LA activity in the course of cold crystalloid cardioplegia.

Animals↗
PubMed1983

Electrical behavior of the heart following high-potassium cardioplegia.

The electrical activity of the heart was studied in 25 patients undergoing elective coronary artery bypass grafting. Simultaneous surface electrocardiograms and bipolar atrial electrograms were monitored continuously from the onset of cardioplegic arrest until normal sinus rhythm was reestablished. Several observations were made. (1) Administration of cardioplegia promptly induced and maintained ventricular arrest in all patients. (2) Atrial activity was seen in 23 patients during global ischemia. (3) Following unclamping, the first sustained rhythm was atrial in 22 patients and was associated initially with high-grade atrioventricular block progressing to 1:1 conduction after a mean reperfusion time of 23 minutes. (4) The time required for complete electrical recovery varied directly with the cross-clamp time and the amount of cardioplegic solution used. (5) Only 3 patients required ventricular defibrillation. (6) In the postoperative period, supraventricular tachyarrhythmias developed in 6 patients. Their occurrence appeared to be related to prolonged atrial activity during the cross-clamp period. Although cardioplegia administration maintained ventricular arrest, sustained atrial activity often was present, perhaps implying inadequate atrial protection and predisposing to atrial arrhythmias. Normal sinus rhythm was reestablished spontaneously in all patients. The atrial electrogram proved essential in the precise intraoperative recognition of cardiac rhythm.

Adult↗
PubMed1983

Persistent atrial activity during cardioplegic arrest: a possible factor in the etiology of postoperative supraventricular tachyarrhythmias.

We assessed the relationship between the duration of atrial activity during the cross-clamp period and the postoperative occurrence of supraventricular tachyarrhythmias in 50 patients undergoing elective coronary bypass operation. The atrial electrical activity was monitored continuously by means of a bipolar atrial electrogram from the onset of cardioplegic administration until removal of the aortic cross-clamp. While ventricular arrest was induced promptly and maintained in all patients, sustained atrial activity was observed in 44 out of 50 patients during the cross-clamp period. In the postoperative period, supraventricular tachyarrhythmias developed in 15 patients (Group 1). Thirty-five patients (Group 2) were free from such tachyarrhythmias. There was no significant difference between the two groups with respect to cross-clamp time, bypass time, amount of cardioplegic solution used, or number of grafts per patient. The mean duration of atrial activity during cardioplegic arrest, however, was significantly longer in Group 1 than in Group 2 (46 +/- 4.7 minutes versus 22.6 +/- 4.0 minutes, respectively, p less than 0.001). None of the 6 patients in whom atrial activity was completely abolished experienced supraventricular tachyarrhythmias. The strong correlation observed between the duration of atrial activity during cardioplegic arrest and the incidence of postoperative supraventricular tachyarrhythmias suggests the possibility that these arrhythmias may be a manifestation of inadequate atrial protection during global myocardial ischemia.

Arrhythmias, Cardiac↗
PubMed1983

Atrial electrical activity and its suppression during cardioplegic arrest in pigs.

Right atrial electrical activity and myocardial temperatures of all four chambers were monitored during a 1 hour period of cardioplegic arrest in 20 pigs subjected to different methods of venous cannulation and cardiac cooling. Myocardial protection was provided by systemic hypothermia (28 degrees C) and intermittent intra-aortic administration of cold (4 degrees C) hyperkalemic (20 mEq/L) crystalloid cardioplegia. The use of a single right atrial cannula for venous drainage was associated with sustained atrial activity (50 +/- 5.5 minutes) during cardioplegic arrest and the warmest right atrial (27 degrees +/- 0.2 degrees C) and right ventricular (20.5 degrees +/- 0.4 degrees C) temperatures. Separate caval cannulation with snaring and right atrial venting decreased right atrial and ventricular temperatures marginally (25.3 degrees +/- 0.5 degrees C and 19.1 degrees +/- 0.4 degrees C, respectively, p less than 0.05) but did not significantly alter the duration of atrial electrical activity (42.2 +/- 2.5 minutes, p greater than 0.05). Addition of an extracavitary right atrial drip of cold (4 degrees C) saline, 750 ml for the 1 hour aortic clamping period, reduced right atrial temperature (22.8 degrees +/- 0.4 degrees C) and activity (24.8 +/- 6.3 minutes) to a significant extent. Intracavitary irrigation of the right atrium with cold saline, in the presence of snared double caval cannulas, decreased right atrial and ventricular temperatures most dramatically (17.0 degrees +/- 0.5 degrees C and 17.5 degrees +/- 0.3 degrees C, respectively, p less than 0.05), reduced the duration of atrial electrical activity by 84% (to 8 +/- 3.9 minutes, p less than 0.01), and diminished the total number of atrial contractions per hour of aortic clamping by 88%. It is concluded that intracavitary right atrial cooling with separate snared caval cannulation is the most effective method of ensuring atrial inactivity and prolonged right heart hypothermia during cardioplegic arrest.

Animals↗
PubMed1980

Ventricular aneurysm: false or True? An important distinction.

A case of ventricular false aneurysm withe the typical clinical, radiological, electrocardiographic, and angiographic features of this entity is presented. The distinction between false ventricular aneurysm and true aneurysm is discussed. This distinction is important because of the propensity of false aneurysms to rupture. An early diastolic murmur was present prior to, but not after, resection of the aneurysmal sac. A theory as to the origin of this murmur is offered.

Cardiac Catheterization↗
PubMed1979

Heparin-associated thrombocytopenia: low frequency in 104 patients treated with heparin of intestinal mucosal origin.

A prospective study of 104 patients receiving heparin obtained from porcine intestinal mucosa for 4 or more days was conducted to determine the frequency of associated significant thrombocytopenia (platelet count less than 100 x 10(9)/I on 2 consecutive days). No episodes of significant thrombocytopenia were identified in the 13 patients receiving heparin by continuous intravenous infusion for a mean of 8.0 days or in the 38 patients receiving heparin subcutaneously for a mean of 9.9 days. In 1 of the 26 patients receiving heparin as intermittent intravenous boluses for a mean of 8.2 days significant thrombocytopenia developed; this patient had laboratory evidence of disseminated intravascular coagulation. In none of the 17 patients receiving uninterrupted heparin therapy for 4 or more days by more than one route of administration but for less than 4 days by any single route did significant heparin-associated thrombocytopenia develop. Of the 104 patients 13 had one or more platelet counts of less than 150 x 10(9)/I, but in most it was not possible to definitely relate the thrombocytopenia to the heparin therapy. Platelets in normal platelet-rich plasma did not aggregate when heparin and serum from patients with thrombocytopenia were added. The frequency of heparin-associated thrombocytopenia noted in this study was considerably lower than that reported previously.

Aged↗
PubMed1979

Vacuolization of the neutrophil in bacteremia.

We evaluated cytoplasmic vacuolization in the neutrophil as a marker of bacterial infection. We sought this phenomenon in 96 septic and nonseptic subjects. No significant differences in the extent of vacuolization were found among control patients, toxic patients without bacterial infections, and patients with bacterial infections in the absence of documented bacteremia. The extent of vacuolization was significantly greater in bacteremic patients when compared with all other groups, including patients with bacterial infection without bacteremia. However, extensive vacuolization in the neutrophils of some patients in toxic states not apparently caused by bacterial infection was noted. The phenomenon seems useful as a diagnostic test to identify bacteremia, although it may be less specific than previously thought.

Capillaries↗
PubMedDate not supplied

Persistent atrial activity during cardioplegic arrest: suppression by verapamil.

Postoperative supraventricular tachyarrhythmia may occur more often in patients with persistent atrial activity during hyperkalemic hypothermic cardioplegic arrest. Cannulation of both venae cavae with simultaneous right atrial intra-cavitary cooling reduces atrial activity but is cumbersome. To evaluate pharmacologically-induced atrial arrest using verapamil, bipolar ventricular and right atrial electrograms were recorded in 12 dogs during one hour of hyperkalemic hypothermic cardioplegic arrest and cardiopulmonary bypass using single caval cannula. Group I (n = 6) received hyperkalemic hypothermic cardioplegic solution (4 degrees C) (20 mEq/1 K+) with verapamil (1 mg/L) by intermittent intra-aortic infusion during systemic hypothermia (28 degrees C). Group II (n = 6) received hyperkalemic hypothermic cardioplegia without verapamil. The percentage of time atrial activity was present (greater than 10 beats/min) in Group I, was significantly less than in Group II. Similarly the total number of atrial beats in Group I was less than in Group II. Recovery of normal sinus rhythm during reperfusion was prolonged in Group I in comparison to Group II. Verapamil induces significant and persistent atrial suppression during hyperkalemic hypothermic cardioplegic arrest but prolongs recovery of normal sinus rhythm during reperfusion. It remains to be established clinically whether verapamil-induced atrial suppression is associated with less postoperative supraventricular tachyarrhythmia. The potential disadvantage of prolonged sinus node recovery time must also be assessed.

Animals↗