Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Patent
1991-06-27
1993-11-16
Kamm, William E.
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
128696, 128710, A61N 137
Patent
active
052614018
DESCRIPTION:
BRIEF SUMMARY
This invention relates to ambulatory cardiac diagnostic units, that is to units which may be worn by a patient and which serve to monitor the patient's heart with a view to providing data which may be used to diagnose heart malfunction.
It is known for patients having certain heart disorders to be fitted with a pacemaker which may be implanted by surgery and which provides electrical outputs for pacing beating of the heart. It is also known to monitor the electrocardiogram of a patient over a the period of a day by using a 24-hour tape loop recording device which may be worn by the user (N. J. Holter, "New Method for Heart Studies: Continuous Electrocardiography of Active Subjects", Science 134:1214, 1961).
However, the shortcomings of such Holter monitoring has been apparent in many clinical situations for some time, and there has been a need for some form of recording pacemaker. The demand for such a recording pacemaker would be considerable, particularly for the diagnosis of heart disease causing infrequent disturbances and unexplained syncope (D. B. Shaw, C. A. Kekwick, D. Veale, T. W. Whistance, "Unexplained Syncope", Pace July 6, 1983). Current data emphasises the difficulty in diagnosis of heart disease under such conditions, even after complex studies in hospital. Most pacing centres which do not have a special interest in sinus node disease do not have the time or facilities to undertake prolonged investigations. In the absence of any clear evidence of any major sinus node function disturbance the patient's symptoms are commonly labelled as "non-cardiac". However the following publications suggest that further follow-up investigations would indicate that potential benefit would result from pacing with an appropriate unit: R. A. Winkle "Long-term electrocardiographic and event recorders for the diagnosis and treatment of cardiac arrhythmias", Circulation (Supplement) 75: III-53, 1987; J. T. Bigger "Perspectives on long-term recording and monitoring", Circulation (Supplement) 75: III-58, 1987; D. B. Shaw, T. W. Whistance, "Clever Pacemakers", Hospital Update, November 1986. U.S. Pat. Nos. 4,183,354, 4,250,888, 4,363,397 and 4,513,743 disclose various forms of diagnostic recorder but none of these matches the criteria which are believed to be of importance in providing satisfactory diagnosis under a variety of conditions.
It is an object of the invention to provide a generally improved form of ambulatory cardiac diagnostic unit.
According to the present invention there is provided an ambulatory cardiac diagnostic unit comprising recording means for recording data indicative of cardiac function for subsequent analysis, the recording means being adapted to record data representative of electrical activity of the heart measured over a cardiac event monitoring period, and control means for controlling recording over said cardiac event monitoring period in response to sensing of a cardiac event, characterised in that the unit further comprises pacing means adapted to initiate pacing of the heart under control of said control means such that following sensing of a heart malfunctiuon pacing of the heart is initiated after recording of data indicative of a cardiac event has taken place over said cardiac event monitoring period.
Preferably the control means is adapted to control the pacing means so as to give demand pacing for a predetermined duration following said cardiac event monitoring period.
The recording means may also be adapted to record data indicative of a second cardiac function, such as intracardiac pressure (or rate of change of pressure) or intracardiac impedance.
Preferably both signals are used in combination to provide reliable detection of heartbeats. Furthermore the unit may be adapted to detect whether "capture" has occurred during pacing.
Conveniently the signals are sensed using a single intracardiac catheter. Furthermore the unit may be adapted to measure the interval between sensed beats, and optionally to store a histogram of the time intervals between successive beats. This time in
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Baker James
Horwood John M.
Prosser Nicola L.
Shaw David B.
Whistance Anthony W. T.
Kamm William E.
Schaetzle Kennedy J.
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