958 F.2d 1053 60 U.S.L.W. 2603, 22 U.S.P.Q.2d 1033 (Cite as: 958 F.2d 1053) ARRHYTHMIA RESEARCH TECHNOLOGY, INC., Plaintiff-Appellant, v. CORAZONIX CORPORATION, Defendant-Appellee. No. 91-1091. United States Court of Appeals, Federal Circuit. March 12, 1992. Rehearing Denied May 5, 1992. Holder of patent directed to analysis of electrocardiographic signals in order to determine certain characteristics of heart function brought infringement suit. The United States District Court for the Northern District of Texas, A. Joe Fish, and John B. Tolle, JJ., declared patent invalid for failure to claim statutory subject matter, and plaintiff appealed. The Court of Appeals, Pauline Newman, Circuit Judge, held that process and apparatus claims satisfied criteria for statutory subject matter. Reversed and remanded. Rader, Circuit Judge, filed concurring opinion. *1054 John F. Flannery, Fitch, Even, Tabin & Flannery, Chicago, Ill., argued for plaintiff-appellant. With him on the brief was Robert J. Fox. Robert W. Turner, Jones, Day, Reavis & Pogue, Dallas, Tex., argued for defendant-appellee. With him on the brief was John E. Vick, Jr., Hubbard, Thurman, Tucker & Harris, Dallas, Tex. Before NEWMAN, LOURIE and RADER, Circuit Judges. PAULINE NEWMAN, Circuit Judge. Arrhythmia Research Technology, Inc. appeals the grant of summary judgment by the United States District Court for the Northern District of Texas [FN1] declaring United States Patent No. 4,422,459 to Michael B. Simson (the '459 or Simson patent) invalid for failure to claim statutory subject matter under 35 U.S.C. s 101. The court did not decide the question of infringement. FN1. Arrhythmia Research Technology, Inc. v. Corazonix Corp., No. CA 3-88- 1745-AJ (N.D.Tex. October 3, 1990), reconsid. denied (November 8, 1990) (Order); appeal authorized (November 9, 1990) (Order). We conclude that the claimed subject matter is statutory interms of section 101. The judgment of invalidity on this ground is reversed. The Simson Invention The invention claimed in the '459 patent is directed to the analysis of electrocardiographic signals in order to determine certain characteristics of the heart function. In the hours immediately after a heart attack (myocardial infarction) the victim is particularly vulnerable to an acute type of heart arrhythmia known as ventricular tachycardia. Ventricular tachycardia leads quickly to ventricular fibrillation, in which the heart ceases effectively to pump blood through the body. Arrhythmia Research states that 15-25% of heart attack victims are at high risk for ventricular tachycardia. It can be treated or prevented with certain drugs, but these drugs have undesirable and sometimes dangerous side effects. Dr. Simson, a cardiologist, sought a solution to the problem of determining which heart attack victims are at high risk for ventricular tachycardia, so that these persons can be carefully monitored and appropriately treated. Heart activity is monitored by means of an electrocardiograph device, whereby electrodes attached to the patient's body detect the heart's electrical signals in accordance with the various phases of heart activity. The signals can be displayed in wave form on a monitor and/or recorded on a chart. It was known that in patients subject to ventricular tachycardia certain anomalous waves having very low amplitude and high frequency, known as "late potentials," appear toward the end of the QRS [FN2] segment of the electrocardiographic signal, that is, late in the ventricular contraction cycle. Dr. Simson's method of detecting and measuring these late potentials in the QRS complex, and associated apparatus, are the subject of the '459 patent. FN2. According to Arrhythmia Research, the QRS complex lasts about one tenth of a second and arises from the depolarization of the ventricles prior to contraction. *1055 The '459 patent specification describes these procedures. Certain of the heart attack patient's electrocardiographic signals, those obtained from electrodes designated as X, Y, and Z leads, are converted from analog to digital values, and a composite digital representation of the QRS segment is obtained by selecting and averaging a large number of the patient's QRS waveforms. The anterior portion of the composite QRS waveform is first isolated, and then processed by a digital high pass filter in reverse time order; that is, backwards. This step of reverse time order filtering is described as the critical feature of the Simson invention, in that it enables detection of the late potentials by eliminating certain perturbationsthat obscure these signals. The root mean square of the reverse time filtered output is then calculated, as described in the specification, to determine the average magnitude of the anterior portion of the QRS complex. Comparison of the output, which is measured in microvolts, with a predetermined level of high frequency energy, indicates whether the patient is subject to ventricular tachycardia. That is, if the root mean square magnitude is less than the predetermined level, then low amplitude, high frequency late potentials have been shown to be present, indicating a higher risk of ventricular tachycardia. If the root mean square value is greater than the predetermined level, high risk for ventricular tachycardia is not indicated. Certain steps of the invention are described as conducted with the aid of a digital computer, and the patent specification sets forth the mathematical formulae that are used to configure (program) the computer. The specification states that dedicated, specific purpose equipment or hard wired logic circuitry can also be used. The district court held that the method and apparatus claims of the Simson patent are directed to a mathematical algorithm, and thus do not define statutory subject matter. Claim 1 is the broadest method claim: 1. A method for analyzing electrocardiograph signals to determine the presence or absence of a predetermined level of high frequency energy in the late QRS signal, comprising the steps of: converting a series of QRS signals to time segments, each segment having a digital value equivalent to the analog value of said signals at said time; applying a portion of said time segments in reverse time order to high pass filter means; determining an arithmetic value of the amplitude of the output of said filter; and comparing said value with said predetermined level. Claim 7 is a representative