Anders Hedman

Right ventricular function before and after an uncomplicated coronary artery bypass graft as assessed by pulsed wave Doppler tissue imaging of the tricuspid annulus

BACKGROUND Right ventricular (RV) function using myocardial velocities before and after a coronary artery bypass graft (CABG) is not known. METHODS Using pulsed wave Doppler tissue imaging, RV function was studied in 35 patients before and after CABG. Patients were followed-up for 1 year after the CABG. Myocardial velocities at the tricuspid annulus at the RV free wall were recorded from the apical 4-chamber views. RESULTS Both the systolic and early diastolic tricuspid annular velocities (TAV) were significantly reduced 1 month after CABG (P <.001 for both). During the follow-up period, there was no improvement in the diastolic TAV. The systolic TAV showed no improvement 3 months after CABG but recovered partially 1 year after the CABG (systolic velocities were 11.8, 8.7, 8.7 and 9.7 cm/s, the early diastolic velocities were 11.0, 8.1, 8.1 and 8.2 cm/s before and 1 month, 3 months and 1 year after the CABG, respectively). The systolic and early diastolic velocities of the interventricular septum were unchanged during the follow-up period. Unlike the right ventricle, the mitral annular systolic velocity was unchanged shortly after CABG and showed signs of improvement after 1 year (6.4, 6.9, 6.8 and 7.3 cm/s respectively before and after CABG). Patients underwent dobutamine stress echocardiography (DSE) before and 3 months after the CABG. The systolic TAV increased significantly during the DSE before CABG (11.8 vs 15.8 cm/s, P <.001). However, the increase in systolic TAV was limited during DSE 3 months after CABG (8.7 vs 9.9 cm/s, P <.05). CONCLUSION RV function, as assessed by TAV, decreased significantly after CABG and the changes were still evident after 1 year. The response of systolic TAV during DSE was more pronounced before CABG than after CABG.

QT Sensing Rate Responsive Pacing Compared to Fixed Rate Ventricular Inhibited Pacing: A Controlled Clinical Study

Eighteen patients, five women and 13 men, fmean age 70 ± S.E.M. 2 years) treated with QT sensing rate responsive pacemakers due to symptomatic high degree AV block took part in a double‐blind study, comparing the rate responsive (TX) mode with fixed rate ventricular inhibited (VVI) pacing. The pacemaker was blindly programmed to either mode in a cross‐over design. During the 1 month period a daily diary of symptoms (chest pain, vertigo, dyspnea, and palpitations) was kept. At the end of each period, a mental stress test and an exercise test were performed. The patient rated the general well‐being and stated a preference for one of the modes. In the TX mode the heart rate was significantly higher at the end of exercise compared with WI (107 ± 4 vs 73 ± 3 bpm; P < 0.001) and the exercise tolerance was improved by 9% (104 ± 8 vs 96 ± 7 W; P < 0.01). The patients reported significantly less dyspnea and fatigue at comparable workloads with TX pacing. During the mental stress test the pacing rate increased by 10% in the TX mode (from 73 ± 2 to 82 ± 4 bpm; P < 0.001). There was a physiological rate variability on 24‐hour Holter monitoring. Ten patients reported a significant improvement in feeling of general well‐being in the TX mode. Eleven patients preferred the TX mode, five patients could not distinguish between the modes and two patients preferred the WI mode due to worsening of angina pectoris with TX pacing. This preference for the TX mode was significant (P < 0.05). The results of this controlled study indicate that TX is preferable to VVI in most cases, but the worsening of angina pectoris in two of the patients and the occurrence of rapid rate oscillations in a third patient are factors that warrant some caution in selecting patients.

Changes in QT and Q-aT Intervals Induced by Mental and Physical Stress with Fixed Rate and Atrial Triggered Ventricular Inhibited Cardiac Pacing

We have investigated the influence of mental stress and physical stress, i.e., exercise, on the QT and Q‐aT intervals (measured from the pacemaker stimulus to the end or the apex, respectively, of the T wave). The study was made on ten patients with high degree atrioventricular block treated with AV universal (DDD) pacemakers. These were programmed to a fixed rate ventricular (VVI) or an atrial triggered (VDD) function for different parts of the study. An arithmetic mental stress test and a bicycle exercise test were performed with each mode of pacing. In the VVI pacing mode, the atrial rate increased by 11% during mental stress and by 46% during exercise. There was a significant shortening of QT and Q‐aT intervals with both types of stress. With VDD pacing, mental stress induced a 12% increase in rate and a significant shortening of QT and Q‐aT. The paced rate increased by 50% during the exercise test. This increase in ventricular rate was associated with the most marked changes in QT and Q‐aT intervals. Thus, both types of stress cause a significant shortening of the QT and Q‐aT interval even in the absence of a simultaneous increase in ventricular rate. When the latter is allowed to increase during VDD pacing, both intervals shorten considerably more. There was a marked inter‐individual variability in the response to both types of stress. These findings are of importance with regard to the QT sensing rate responsive pacemaker which can be expected to respond to mental stress in most patients, but that response might be unpredictable in the individual.

Cardioversion of atrial fibrillation and its effect on right ventricular function as assessed by tricuspid annular motion

In patients with atrial fibrillation, the reduced right ventricular function determined by tricuspid annular motion before cardioversion returns to normal 1 month after successful cardioversion to sinus rhythm. The simplicity of recording the tricuspid annular motion provides an easy opportunity to assess right ventricular function following electroconversion of atrial fibrillation to sinus rhythm.

Changes in Q-T and Q-aT Intervals at Rest and During Exercise With Different Modes of Cardiac Pacing

The influence of heart rate variation on the Q‐T and Q‐aT intervals (measured from the onset of the QRS to the end or the apex, respectively, of the T‐wave) was studied both at rest and during exercise using different modes of pacing. The studies were made on 21 patients with high‐degree atrioventricular block. In seven patients with programmable ventricular inhibited (VVI) pacemakers, an increase in pacing rate during rest produced significant shortening of both Q‐T and Q‐aT. During observations made at rest and during exercise in 14 patients with fixed rate VVI, atrial rate matched asynchronous (VVIm) or atrial triggered (VAT) pacing. Significant shortening of Q‐T and Q‐aT intervals occurred during exercise in all pacing modes, but was greatest with VVIm and VAT. The Q‐T and Q‐aT changes were almost parallel in all situations. For measurements made by two independent observers the coefficient of variation was lower for Q‐aT than for Q‐T (2.2 versus 2.5) and the correlation coefficient was higher (0.96 versus 0.93), indicating easier identification of Q‐aT than of Q‐T. This study indicated that changes in Q‐T and in Q‐aT are influenced by intrinsic factors in addition to the ventricular rate. Atrioventricular synchronization did not seem to influence these changes.

QT Sensing Rate Responsive Pacing and Myocardial Infarction:.: A Case Report

A 65‐year‐old man, treated with the QT sensing rate responsive pacemaker required to manage high degree AV block, sustained a transmural inferior wall myocardial infarction 6 months after the pacemaker implant. The rate response of the pacemaker during the acute phase of the infarction was physiological as evidenced by increased pacing rate during pain and with the gradual decrease in rate during the first postinfarction days. The underlying mechanisms are discussed.

Feasibility of myocardial performance index for evaluation of left ventricular function during dobutamine stress echocardiography before and after coronary artery bypass grafting.

Myocardial performance index (MPI) is a measure of combined systolic and diastolic myocardial function. In patients with coronary artery disease (CAD) an increase in MPI is consistent with myocardial dysfunction. The objectives of this study were to characterize the changes in MPI after coronary artery bypass graft (CABG) at rest and at peak dobutamine stress echocardiography (DSE).

Cardiac Transplant Rejection and Evoked T Wave Amplitude

One of the most important aims of patient follow-up after cardiac transplantation is the early and reliable detection of transplant rejection. At present, this requires careful monitoring by transvenous right ventricular endomyocardial biopsies, usually performed weekly for the first few weeks postoperatively and later with longer intervals. While endomyocardial biopsies are safe and relatively simple in experienced hands, the need for repeated invasive procedures adds significantly to cost and patient discomfort during posttransplant follow-up. Thus, a simple and reliable noninvasive method to detect rejection would indeed be welcome. Over the years, numerous ideas have been introduced, including concepts based on magnetic resonance imaging, positron emission toniography, various echocardiographic measurements (quantitative tissue characterization, changes in left ventricle function indices, Doppler measurements), immunoscintigraphy by means of marked monoclonal antibodies, and labeled lymphocytes in addition to those using electrophysiological parameters.